i had similar problem
i opened control panel then clicked on add/remove programs, then click install/uninstall tab and was amazed at some of the programs i downloaded, mainly ones which i wasn't aware of. click on add/remove button and uninstall programs you are sure you don't need. you may be diverted to the programs websites to completely uninstall (they'll ask u why your uninstalling, few questions, and then u can uninstall)
My computer's running a lot smoothly now, so try and check your programs as regularly as u can
i use win 98 se, don't know exactly how it works in xp but probably will be a similar procedure
amir, July 2004