TechNote

Optimize performance of Photoshop CS4 on Windows XP and Vista

What's covered

Adobe Photoshop options and plug-ins
Image files
Operating system software
Hardware

The performance of Adobe Photoshop CS4 is affected by available random-access memory (RAM) and computer processor speed. Other factors can also affect performance, such as the options you select, system configuration, and the built-in limitations of Photoshop. The maximum file size Photoshop CS4 supports is 300,000 x 300,000 pixels, except for PDF files, which are constrained by a 30,000 x 30,000 pixel, and a 200 x 200 inch limitation.

File size capability for Photoshop CS4:

PSD files: 2 GB
TIFF files: 4 GB

Note: Most applications cannot work with TIFF files over 2 GB.

PSB files: 4 Exabytes (4096 Petabytes, or 4 million Terabytes)
PDF files: 10 GB (pages are limited to a maximum size of 200 inches).

Note: Large Document Format files (.psb) cannot be read by Photoshop 7.0.x or earlier.

Adobe Photoshop options and plug-ins

The options you select and plug-ins you use in Photoshop can affect its performance. The options and plug-ins that most directly affect performance include those covered in this section.

Setting scratch disks

The Photoshop scratch disk is similar to virtual memory. For the best performance, you should set the scratch disk to a defragmented hard disk that has plenty of unused space and fast read/write speeds (rather than a network drive or removable media). Photoshop requires at least 2 GB of free hard-disk space, but more is recommended. If you have more than one hard disk volume, you should specify additional scratch disks. Photoshop CS4 supports up to 64 Exabytes (EB) of scratch disk space on a total of four volumes. (An EB is equal to 1 billion gigabytes.)

Fast RAID 0 arrays are the best option for scratch disks, especially if the array is used exclusively for your scratch disk, is defragmented regularly, and is not your boot volume, especially if your efficiency goes much below 90%. Photoshop CS4 supports up to 64 Exabytes (EB) of scratch disk space on a total of four volumes. (An EB is equal to 1 billion gigabytes.)

Note: Adobe recommends that you set the primary scratch disk to a different hard disk than the one Windows uses for its virtual memory or paging file.

To set the scratch disk:

Choose Edit > Preferences > Performance.
Select the Active box for each hard disk you want to contain a scratch disk.

Note: Unless you have a drive that has considerable space open, and is defragmented regularly, choose more than one drive, if one or more is available.
Click OK.
Restart Photoshop.

Adjusting the cache levels

Photoshop uses image caching to redraw high-resolution images faster. With caching, Photoshop uses low-resolution versions of an image to quickly update the image on-screen as you work. To enable the Cache Levels option, specify the number (1 to 8) of low-resolution versions you want Photoshop to store (cache). The more versions of an image you have Photoshop cache, however, the slower it opens image files. In Photoshop CS4, the default Cache Level setting is 4. Setting the Cache option to 1 disables image caching; only the current screen image is cached. Setting the Cache higher than 4 improves the performance when working on larger images by redrawing them faster.

If you use files that have small pixel dimensions and many (50+) pixel layers, you'll get the best performance if you set the cache to 1 or 2. If you use files that have large pixel dimensions, set the cache higher.

Note: Image caching may cause a less accurate preview. When necessary, view files at 100% to ensure an accurate preview.

To adjust the Cache Levels setting:

Choose Edit > Preferences > Performance.
Enter a value from 1 to 8 in the Cache Levels text box.
Restart Photoshop.

Set Maximize PSD And PSB File Compatibility to Always or Ask

The Maximize PSD And PSB File Compatibility feature increases the size of your file by attaching a flattened copy of your image when you save your image. A small amount of extra data is included in the file when you choose this option that ensures that PSD and PBS files saved in Photoshop will open in earlier versions. Additionally, if you want to use the Edit in Photoshop feature in Photoshop Lightroom, this option needs to be on.

To change the Maximize File Compatibility option:

Choose Photoshop > Preferences > File Handling.
Change Maximize PSD And PSB File Compatibility to one of the following:
- Ask: Prompts you to maximize file compatibility when you save.
- Always: Saves with maximized file compatibility without asking.
- Never: Does not save or prompt you to save with maximized file compatibility.

Image window management

Image windows use more RAM in Photoshop CS4, than in previous versions, and is especially true if the Application Frame is selected. The Application Frame makes every tabbed image the size of the entire monitor. When you open the same number of images that you opened in previous versions of Photoshop, you may now get an Out of RAM error message, or Photoshop might run slowly. If this occurs, close some image windows, and/or turn off Application Frame.

GPU use

Photoshop CS4 leverages the graphics display card's GPU, instead of the computer CPU, to speed its screen redraw. For Photoshop to access the GPU, your display card must contain a GPU that supports OpenGL and has enough RAM to support Photoshop's functions - at least 128 MB, and a display driver that supports OpenGL 2.0 and Shader Model 3.0.

To increase performance when accessing a GPU in Photoshop, update your display driver.

For more information on GPU use in Photoshop CS4, see "GPU and OpenGL Features and Limitations in Photoshop CS4" (TechNote kb404898).

Minimizing palette preview thumbnails

Photoshop requires additional memory to display preview thumbnails in the Layers, Channels, and Paths palette. Photoshop updates the preview thumbnails as you make changes to the image itself. The more preview thumbnails Photoshop displays and the larger the thumbnail you select, the more memory Photoshop requires to draw and update preview thumbnails.

To minimize or turn off palette previews in the Layers, Channels, or Paths palette, select Palette Options from the palette menu. For Thumbnail Size, select the smallest thumbnail size or select None, then click OK.

Out of RAM errors running filters, 3D, Content Aware Scaling, Liquify

When you use the various features which are memory-intensive, such as Content Aware Scaling, 3D, Liquify, and filters such as the Distort filters, on a computer running 32-bit Windows, with low RAM, or low open hard-disk space, Photoshop responds slowly or not at all. These features can require more than the recommended minimum amount of RAM and disk space for Photoshop. If Photoshop responds slowly when you use the these features, increase memory used by Photoshop, or free additional space on the hard disk.

For instructions on how to increase memory used by Photoshop, see "Allocating more memory to Photoshop" in this document.

16-bit and 32-bit functionality

Photoshop CS4 increases the number of features that can be performed on 16-bit images and allows numerous operations to be performed on 32-bit images. However, if your resources are low, reducing your images to 8-bit can improve performance. Note that this reduction will permanently delete the extra bit data from your image.

Bigger Tiles plug-in

The Bigger Tiles plug-in, which is located in the Optional Plug-ins folder on your application DVD folder, is disabled by default. When you enable it by copying it to the Extensions folder under your Photoshop CS4 Plug-ins folder, and by removing the tilde (~) from the file name, you increase the image tile size in Photoshop. You should only enable the plug-in if you have more than 1 GB of RAM installed.

If you enable the plug-in, then Photoshop redraws more data at a time because each tile is larger, and each tile is drawn, complete, at one time. Photoshop takes less time to redraw fewer tiles that are larger than it takes to redraw more tiles that are smaller. Because Photoshop redraws more data at one time, each tile takes longer to be redrawn, so bigger tiles can look like they are redrawing more slowly -- and in fact it can take longer before you see the results on the screen if you're making repeated, small adjustments to a slider in a filter or panel, because an entire tile has to be calculated and drawn before you see anything. But the total time take to compute and draw the final image will be less. Screen updates while painting may also be less smooth with Bigger Tiles installed.

If you spend most of your time painting or rapidly tweaking controls in filters or panels and watching the feedback, then Bigger Tiles is not going to help you. But if you spend your time watching progress bars march across the screen, Bigger Tiles can save you time.

Image files

You can optimize your workflow to improve performance by minimizing file size, editing individual channels, and using image compression selectively. Additionally, because layers and channels add significantly to the size of a file, you can minimize file size by merging layers and deleting channels when you no longer need them. And finally, if you are preparing images for color separation, you can work in RGB mode until you are ready to print and then change the images to CMYK mode. When converted from CMYK to RGB, a file's size should decrease by about 25%.

Minimizing resolution

You can minimize the size of your files by reducing their resolution, which is measured in pixels per inch (ppi). Photoshop requires more memory and disk space to process high-resolution images, which increases the time it takes to display, process, and print them. Increasing the resolution of an image does not always improve the quality of the image, but may instead only increase its file size. You want the resolution of images to be the highest value your printer can use. Resolutions higher than that only add information that your printer can't use, but must process, thereby increasing print times.

The optimal resolution for your images depends on the type of printer you use.

Fixed screen printers, such as imagesetters and laser printers:

For these printers if you are printing continuous-tone images, such as photographs, use a resolution of 1.5 x 2 times the screen frequency, measured in lines per inch (lpi), that you'll use to print the image. For line-art images, such as drawings, use the same value as your printer's resolution, measured in dots per inch (dpi). For example, if the resolution of your printer is 600 dpi, and you plan to print the image using the printer's default screen frequency of 85 lpi, save continuous-tone images at a resolution between 127 ppi (85 lpi x 1.5) and 170 ppi (85 lpi x 2), and save line-art images at a resolution of 600 ppi.

Output - fixed screen printers	Recommended Resolution
300 dpi laser printer	100 ppi
600 dpi laser printer	150 ppi
120 dpi or higher image setter	1.5 - 2 times the screen frequency you specified

Inkjet printers:

180 dpi is a reasonable lower bound for good results regardless of the printer's stated resolution, though images without much detail may look good printed at resolutions as low as 120 dpi. Critical reproductions of images with lots of fine detail could require 300 dpi. Improvements from printing continuous tone images at resolutions beyond approximately 300 dpi becomes increasingly difficult to see. It's also difficult to see much advantage from resizing the image to a specific multiple or fraction of the printer's resolution. A common method is to set the image size (without resampling) to the size of the print they want, and as long as the resulting resolution falls in the 180-400 dpi range, let the printer handle it. If you need more critical results, you can resample the image to an even fraction of the printer's stated resolution (e.g., 360 dpi for printing line art for printing on a 720 x 1440 dpi printer). Both resolutions higher than 300 dpi, and picking an image resolution that is an even fraction of the printer's stated resolution, may be more visible with finely tuned detail line art and text than with continuous tone images.

Fixed pixel printing devices, such as dye sublimation printers and some film recorders (Durst Lambda, Lightjet):

These printing devices provide significantly better quality if the image is the same resolution as the printer or imager, typically 300-400 dpi. Resolutions even slightly higher or lower can significantly degrade results, so it's worth resizing to the exact resolution in Photoshop.

For best printing results, perform a sharpening step appropriate to the specific output device after the last time you use the Image Size command.

To reduce the resolution of an image in Photoshop:

Open the image, then choose Image > Image Size.
In the Image Size dialog box, decrease the Resolution value, and then click OK.

For more detailed information about image resizing and resampling, see "Resize and Crop images in Photoshop and Photoshop Elements" (TechNote 331327).

Purge Undo, Clipboard, or Histories

Undo, Clipboard, and Histories all hold image data. To free RAM, choose Edit > Purge to purge the Undo and Clipboard. Purging Histories can free RAM or scratch disk space depending on how recent your history data is. To reduce disk space usage, reduce the number of History States available in the General preference.

Reduce the number of History states

In Photoshop CS4, each history state that includes an operation that affects the entire image (for example, when you apply Gaussian blur or unsharp mask to the entire image) creates a full copy of your image at its original size. If your initial image is 500 KB, and you apply Gaussian blur to it, your image will need 1 MB of scratch space. If your history states consist of operations that affect only part of the image, such as paint strokes, only the size of the tiles touched by the strokes are added to the image size. If you count up the number of histories you have where operations have affected the entire image, and multiply your original image size by that number, you'll have an approximate amount of scratch disk space needed by the image. If you have applied levels, a reduce noise filter, and an unsharp mask filter to your entire image 5 MB in size, the image will need 20 MB of scratch space. When you reduce the number of History states available, you potentially reduce the number of copies of your image using scratch space.

Reduce patterns and brush tips

If you need to reduce your scratch disk overhead, you can minimize the number of patterns and brush tips you use in each of your presets, and you can reduce the number of patterns you use in your image's Layer Styles (as applied with the Bevel and Emboss Texture or in the Pattern Overlay). Each small pattern and sampled brush in the presets uses at least one tile for storage. Patterns used in Layer Styles use extra RAM as well.

The full set of original patterns are in the preset labeled Patterns. Select it from the pop-up menu in the Preset Manager.

Minimizing the number of layers

Layers are fundamental to working in Photoshop, but they also increase file sizes and redraw time because Photoshop recomposes each layer after each change in the image. After you have completed changes to layers, you can flatten (merge) them to reduce the size of a file. You should also make sure to remove blank layers from the file since they too increase its size. It is important to remember that Photoshop does not let you separate layers after merging them. Instead, you can either use the Undo command or you can use the History palette to reverse a merge.

If you do not need to frequently change some of your layers, you may want to convert layers or layer sets into Smart Objects, to save disk space and help increase speed.

To flatten all layers in a file, choose Layer > Flatten Image.
To merge a layer with the layer below it:
1. In the Layers palette, select the layer above the layer with which you want to merge it.
2. Choose Layer > Merge Down.

Flattening TIFF files

Photoshop allows layers to be saved in TIFF files. Layered TIFF files are larger than flattened TIFF files and require more resources for processing and printing. If you work with a layered TIFF file, save the original layered file as an Adobe Photoshop (.psd) file; then, when you are ready to save the file in TIFF format, save a copy without layers.

Using image compression

Although compressed files generally have small file sizes, Photoshop may take longer to open or save them. With the exception of images saved in Photoshop format, Photoshop must decompress a file to open it and then recompress the file to save it. The BMP, CompuServe GIF, JPEG, Photoshop, Photoshop EPS, Photoshop PDF, and TIFF formats all can be saved with compression. In addition, Photoshop enables you to specify a compression method for TIFF layers in the TIFF Options window. You can improve performance by saving your file in compressed Photoshop format (a compression format in which there is no data loss) as you work, and then save your file in the format you want when you are finished editing the image.

To save an image without compression from Photoshop, choose File > Save As, select the format you want, and then select the No Compression option in the format Options dialog box. For example, select the TIFF format, and in the TIFF Options dialog box, select None for Image Compression.

Editing individual channels

Photoshop requires less memory to apply a filter to a single channel than it does to apply a filter to multiple channels or to an entire image (composite channel). In a flattened image, each RGB channel is about one-third the size of the file; each CMYK channel is about one-fourth the size. To edit a single channel, select the channel you want to edit in the Channels palette.

Using the Filter Gallery and applying filters to individual channels

The Filter Gallery in Photoshop CS4 allows you to test one or more filters on an image before applying the effect(s), which can save considerable time.

Dragging and dropping between files

Dragging and dropping layers or files is more efficient than copying and pasting them. Dragging bypasses the clipboard and transfers data directly. Copying and pasting can potentially involve more data transfer and is much less efficient.

Operating system software

By customizing your operating system so it runs efficiently, you not only increase the amount of system resources available to applications, but also ensure that your applications run efficiently. Optimizing your hard drive and virtual memory, organizing or removing temporary files, and disabling unnecessary applications running in the background improves performance.

Allocating more memory to Photoshop

Photoshop uses random-access memory (RAM) to process image information. The more RAM available to Photoshop, the faster Photoshop can process image information. Other open applications and startup programs decrease the amount of memory potentially available to Photoshop. Quitting applications or startup items you are not using makes more memory available to Photoshop.

To allocate more memory to Photoshop:

Choose Edit > Preferences >Performance.
In the Memory Usage section, increase the Let Photoshop Use percentage, and click OK.
Restart Photoshop.

Allocating memory with 64-bit processors

Photoshop CS4 installs both a 32-bit and a 64-bit version when you install on a 64-bit version of Windows Vista and Windows XP. If you use the 32-bit version of Windows, Photoshop only installs the 32-bit version.

If you run Windows Vista, upgrade to Service Pack 1 for better performance.

Note: Although 64-bit Photoshop CS4 was not thoroughly tested under Windows XP64, and therefore is not supported, it should run.

Photoshop installs a 32-bit and a 64-bit shortcut into the Start Menu. If you need to manually run the application, the 32-bit version is the photoshop.exe file, in the Program Files (x86)/Adobe/Adobe Photoshop CS4 folder, and the 64-bit version is the photoshop.exe file in the Program Files/Adobe/Adobe Photoshop CS4 folder.

Third party plug-ins written for 32-bit versions of Windows will not work when you run the 64-bit version of Photoshop. If you need to use plug-ins that haven't been updated, run the 32-bit version of Photoshop. When you are done using the plug-ins, close the 32-bit version, and run the 64-bit version. Contact the plug-in manufacturer for information about any updates.

Although the 64-bit version of Photoshop will speed up some operations, it won't speed all of them, nor will it speed the operation equally. Generally, operations will run approximately 8-12% faster. Overall, processor speed is not the main advantage of using the 64-bit version.

The primary advantage of using the 64-bit version is to access amounts of RAM beyond what Photoshop can access when the 32-bit version is run. You can take advantage of more than 4 GB of RAM only when you are on 64-bit Windows, using 64-bit Photoshop. If you use files large enough to need more than 4 GB of RAM, and you have enough RAM, all the processing you perform on your large images can be done in RAM, instead of swapping out to the hard disk.

This table lists the amount of RAM available to Photoshop with the different versions of Windows:

Photoshop Version	Windows Version	Manximum amount of RAM that Photoshop can use
32-bit	32-bit	1.7 GB
32-bit	64-bit	3.2 GB
64-bit	64-bit	as much RAM as you can fit into your computer.

The default RAM allocation setting is 70%. This setting should be optimal for most users. To get the ideal RAM allocation setting for your system, change the RAM allocation in 5% increments and watch the performance of Photoshop in the Performance Monitor. You must quit and restart Photoshop after each change to see the change take effect.

The available RAM shown in the Performance preference automatically deducts an amount that is reserved for the operating system from the total RAM in your computer. You shouldn't set the percentage of RAM to be used by Photoshop to 100% because other applications which run at the same time as Photoshop (for example, Adobe Bridge) need a share of the available RAM. Some applications use more RAM than you might expect. For example, web browsers can use 20-30 MB of RAM, and music players can use 20-50 MB RAM. Watch the Performance Monitor to view the RAM allocations on your computer.

Watch your efficiency indicator while you work in Photoshop to determine the amount of RAM you'll need to keep your images in RAM. The efficiency indicator is available from the pop-up menu on the status bar of your image or from the Palette Options on the Info Palette pop-up menu. When the efficiency indicator goes much below 90%, you can increase performance by changing your RAM allocation, adding RAM, or setting your scratch disk to write to a RAID Array.

It is unlikely that Photoshop will respond well if you assign 100% of your RAM to Photoshop; this leads to Out of RAM errors. If this occurs, set the RAM allocation to 85-90%, and retest. If you still have problems, bump the RAM allocation down by 5% increments until the errors stop displaying.

Check your system for damaged fonts

If there is a damaged font on your system and you have WYSIWYG font preview turned on, your computer can slow significantly. If you turn off font preview and your computer performance improves significantly, test for a damaged font. See the Additional information section below for more information on how to troubleshoot fonts.

Temporary files

When you work in an application, a copy of your data file is stored temporarily on the hard drive. Many applications create .tmp files and then delete them when you quit the application. Crashes or system errors, however, may prevent an application from deleting these files. These files can build up over time, taking up disk space and causing problems. From time to time, you should quit all programs and remove all temporary files. To safely remove temporary files and any other files that are no longer being used, run Disk Cleanup.

To run Disk Cleanup:

Do one of the following:
- On Windows XP: Choose Start > Programs > Accessories > System Tools > Disk Cleanup.
- On Windows Vista: Choose Start, and type Disk Cleanup in the Search text box. Select Disk Cleanup from the Programs list.
Choose a drive to cleanup, if appropriate.
Choose types of files to delete. You may select all file types to clean your system completely, but you must select Temporary Files at a minimum.
Click OK.
Confirm that you want to permanently delete these files.

Optimizing and defragmenting hard disks

Over time, the computer's hard disk can become damaged or fragmented (unavailable in a large contiguous block). If there is not enough contiguous space for the system to save a file, it saves pieces of the file to different locations on the disk. It takes an application longer to read a fragmented file whose pieces are saved in several locations.

To optimize and defragment the hard disk: Use the Disk Defragmenter:

On Windows XP: Choose Start > All Programs > Accessories > System Tools > Disk Defragmenter.
On Windows Vista: Choose Start, type Disk Defragmenter in the Search text box. Select Disk Defragmenter under Programs.

Windows virtual memory and Photoshop scratch disk files

Virtual memory allows your system to use hard-disk space to store information normally stored in memory (RAM). Because it takes longer to access information on a hard disk than it does to access information in memory, using a portion of the hard disk as virtual memory can decrease performance. In addition, Photoshop cannot use the hard-disk space the system uses for virtual memory for its scratch disk files, which it uses to store image information as you work. If you need more memory to work in Photoshop, Adobe Systems recommends installing more RAM.

Specifying a fixed virtual memory setting helps prevent Photoshop scratch disk files from competing for the same space with virtual memory, especially if you set the virtual memory setting on a different drive than the primary scratch disk. For both kinds of virtual memory, be sure to use a drive with enough free, uncompressed space. RAID 0 partitions provide the best possible performance as Photoshop scratch disks.

If you use a disk or RAID array only for Photoshop scratch disk files, fragmentation is rarely a concern, as they don't become significantly fragmented. Fragmentation is much more likely to be an issue if you use a single disk for everything or if you have permanent files and the Photoshop scratch disk sharing a volume, especially if there's not a lot of free space. In this case, defragmenting the disk can make a significant difference.

See the above section "Optimizing and defragmenting hard disks" for more information.

To change Virtual Memory in Windows XP:

Quit all applications.
Choose Start > Settings > Control Panel and double-click System.
Click the Advanced tab and then select Settings in the Performance section.
Click the Advanced tab, and in the Virtual memory section, click Change.
From the Drive list, select a hard drive that has 1.5 times the amount of your computer's installed RAM. For example, if your computer has 2 GB of RAM, select a hard drive that has at least 4 GB of free hard drive space. For best performance, choose a hard drive not used for the Photoshop scratch disk(s).
In the Paging File Size for Selected Drive section, select Custom size, and in the Initial Size box, enter a value equal to the twice the amount of your computer's installed RAM.
In the Maximum Size box, enter a value equal to four times the amount of your computer's installed RAM.
Click Set and then click OK.

Note: For the best performance, the Paging File should be on a separate, empty, de-fragmented hard disk.
Click to close the System Control Panel Applet.
To restart Windows, click Yes in the System Settings Change dialog box.

To change Virtual Memory in Windows Vista:

Quit all applications.
Choose Start > Control Panel, and double-click System.
Choose Advanced System Settings in the Tasks list.
Select the Advanced tab and click Settings in the Performance section.
Select the Advanced tab and click Change.
Usually it's best to allow Windows to manage the paging file. However, for the better performance, the Windows paging file should be on a different hard disk from the Photoshop scratch disk. To manage the paging file manually, set it to a different drive from the Photoshop scratch disk by deselecting Automatically Manage Paging File Size For All Drives.
Click each hard disk letter to show the available space on that drive. Select a hard drive that has three times the amount of your computer's installed RAM and that doesn't contain a scratch disk.
Select Custom Size, and type the amount of your physical RAM plus 300 MB in the Initial Size box. Type 3 times the amount of your computer's installed RAM into the Maximum Size box. Click Set, and then click OK. Continue to click OK to exit all dialog boxes.
Restart your computer: If you have applications open, select Restart Later, close your applications, then restart Windows. Otherwise, click Restart Now.

Applications running in the background

Some applications may compete for memory with Photoshop and cause slowdowns or system errors. Before starting Photoshop, disable other applications, including startup items (items that start automatically with Windows).

In Windows XP:

Disable startup items:

Quit all applications.
Choose Start > Run, and type msconfig in the Open box. Click OK.
Click the Startup tab, and click Disable All.
Select any startup items that are essential for testing the problem. If you are unsure whether an item is essential, leave it deselected (disabled).
Click OK, and restart Windows.

Note: Depending on settings in the System Configuration utility, a System Configuration utility dialog box may appear after the restart asking you if you want to continue in Selective Startup mode. If this occurs, click OK once to close the message dialog box. Click OK again to quit the System Configuration utility. Click Exit Without Restart.
Right-click icons in the Notification Area (called the System Tray in earlier versions of Windows) to close or disable any startup items that are still active.

Then, try to re-create the problem:

If the performance of Photoshop increases, one or more of the disabled startup items is conflicting with Photoshop. Reenable startup items one at a time, testing each time until you determine which item conflicts with Photoshop. Then contact that item's developer for an update, if available.
If the performance doesn't change, startup items aren't the cause and you can reenable them.

To reenable startup items:

Choose Start > Run, and type msconfig in the Open box. Click OK.
Click the Startup tab, and click Enable All.
Click OK, and restart Windows.

In Windows Vista:

Quit all applications.
Choose Start, type msconfig in the Search text box, and press Enter.
Write down all unselected items under the Startup and Services tabs.
Click the General tab, and choose Selective Startup.
Click the Startup tab and select Disable All.
Click Apply, and restart Windows for the changes to take effect.

Note: Upon restart, you'll be notified that the System Configuration utility has made changes to the way that Windows starts up. Click OK. When the System Configuration utility appears, click Cancel.
Right-click icons in the Notification Area and close or disable any startup items that are still active.

Then, try to re-create the problem:

If the performance of Photoshop increases, one or more of the disabled startup items is conflicting with Photoshop. Reenable startup items one at a time, testing each time until you determine which item conflicts with Photoshop. Then contact that item's developer for an update, if available.
If the performance doesn't change, startup items aren't the cause and you can reenable them.

To reenable startup items:

Choose Start > and type msconfig in the Search text box, and press Enter.
Click the Startup tab, and click Enable All.
Click OK, and restart Windows Vista.

Hardware

Photoshop performance is limited by the hardware you use: faster the processors or hard disks allow for faster image information processing. Other hardware options, such as installing additional RAM, using a multiprocessor system, or using optimized and defragmented disks, can also improve performance.

Processor speed

Image information processing speed is limited by the speed of the computer's processor, or CPU (Central Processing Unit). Photoshop requires a 1.8GHz or faster processor.

All Photoshop features are faster on a multiprocessor system, although some can take greater advantage of the multiprocessor system's capabilities than others.

Installed RAM

Photoshop requires that the available RAM is several times the size of each image, depending on how you use the application. If Photoshop has insufficient memory, it uses hard-disk space (scratch disk) to process information. Because accessing information in memory is faster than accessing information on a hard disk, Photoshop is fastest when it can process all or most image information in memory (RAM), without using the scratch disk. Allocate enough memory to Photoshop to accommodate your largest image file.

To check use of memory for Photoshop, open the Efficiency Indicator by choosing Show > Efficiency from the pop-up menu on the status bar of your image. This indicator displays the percentage of time Photoshop spends completing an operation instead of reading or writing the scratch disk. If the value is less than 95-100%, then Photoshop is using the scratch disk and, therefore, is operating more slowly than necessary. If the efficiency is around 90%, you'll see a large performance increase by changing your RAM allocation or adding RAM.

Hard disks

Since Photoshop reads and writes image information while working on an image, the faster the access speed of the disk containing your image or the scratch disk, the faster Photoshop can process image information. To improve Photoshop performance, work on files saved on disks with fast access speeds, such as an internal hard disk, rather than those with slow access speeds, such as a network server (hard disk accessed over a network) or removable media. Removable media often have slower access times and are more easily damaged than nonremovable disks.