General Advice for Making Better Use of RAM

• Remove DLLs from cache memory. If you notice your system running slowly after XP has been running for some time, or if your RAM seems to be getting low for some reason, the culprit may be left-behind DLLs from programs that are no longer running, but that XP still keeps in memory. Sometimes XP keeps DLLs in cache memory even when the program that required them is no longer running, and this cuts down on the memory available to other applications.
You can use a simple Registry hack to have XP automatically remove from cache memory DLLs that are no longer needed by programs. Run the Registry Editor and go to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer. Create a new DWORD value named AlwaysUnloadDll, and give it a data value of 1. Exit the Registry and reboot for the new setting to take effect. Note that this setting may cause problems with some programs. Some Windows programs—especially older and 16-bit programs—may issue error messages with this setting in effect; so if that starts happening, delete the new key or give it a value of 0.
• Reduce the number of colors. Using 32-bit color takes up a great deal more memory than 16-bit color, and it also puts a greater strain on your processor. If you primarily use business applications such as word processors and spreadsheets, you most likely won't notice a different between 16-bit and 32-bit color, so going with 16-bit color is a good bet. To change your color depth, right-click on the desktop, choose Properties->Settings, and in the Color Quality box choose 16 bit.
• Avoid DOS applications. DOS applications don't allow XP to manage memory properly, and they hold onto the memory they use, not allowing it to be swapped out for use for other programs or processes. If you use any DOS applications, replace them with Windows versions.
• Reduce the icons on your desktop. Every icon on your desktop uses up memory. Delete icons you don't use regularly. Run the Clean Desktop Wizard, which will automatically delete icons that you don't regularly use. Right-click on the Desktop and choose Properties ->Desktop ->Customize Desktop ->Clean Desktop Now. A wizard will step you through the process of deleting unused icons. If you want the wizard to run every 60 days, check "Run Desktop Wizard every 60 days."
• Reduce the applications and services running in the background. You may have many programs and services running in the background, without realizing it. Look at your Notification area, and see if there are any programs running that you don't require. Shut them down, and make sure that they don't load at startup. Also, XP frequently starts services on startup that you might not need . For example, if you don't use a wireless network card, you don't need the Wireless Zero Configuration service.