[HKLM\SYSTEM\CurrentControlSet\Control\SessionManager\MemoryManagement] “IoPageLockLimit”

Myth – “Increasing the IOPageLockLimit will lock more memory for exclusive access by the kernel, improving performance.”

Reality – “Indeed, it does do this but only in an RTM Windows 2000 machine. It does absolutely nothing in Windows 2000 Service Pack 1 and up, and absolutely nothing in Windows XP. This makes it effectively useless, since no one in their right minds would be running RTM Windows 2000. The RTM kernel references IoPageLockLimit. The SP1 kernel does not. Neither do any subsequent editions of the kernel; neither does the XP kernel in any of its incarnations.”
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[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer] “AlwaysUnloadDLL”

Myth – “Enabling AlwaysUnloadDLL frees up more memory and improves performance.”

Reality – “Adding this Registry Key in Windows 2000 or XP has no effect since this registry key is no longer supported in Microsoft Windows 2000 or later. The Shell automatically unloads a DLL when its usage count is zero, but only after the DLL has not been used for a period of time. This inactive period might be unacceptably long at times, especially when a Shell extension DLL is being debugged. For operating systems prior to Windows 2000, you can shorten the inactive period by adding this registry key.”
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Just take a look at the following page 4 more myth’s:
http://home.comcast.net/~SupportCD/XPMyths.html

If you want to revive an old computer, put Linux on it. You can have the latest versions of any distro and have it as fast as any new computer.