SERVICE PACKS normally fix things,
at least in theory. But changes to Windows XP's memory management
system in XP Service Pack 1 can have the opposite effect.
Thankfully there is a patch.
The problem comes about because of the way that the memory
management system deals with memory allocation. If a program
allocates and deallocates large blocks of memory too often that
will cause Windows XP SP1 to snarl up.
However, although there is a fix, you shouldn't apply it unless
you're definitely having this problem. Microsoft is so sure about
you not installing the patch unless it's absolutely necessary that
it hasn't even made the patch available on its site. You have to
phone the company up and hope that it agrees that you need the
Microsoft Knowledge Base Article - 815411