I got this info about the registry key from TechRepublic: http://techrepublic.com.com/5100-6270_11-5165773.html?tag=e064# although I did read some similar info from MaximumPC magazine http://www.maximumpc.com/
One of those tips to help out windows xp run quicker:
Delete any files in C:\Windows\Prefetch
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\PrefetchParameters