I have reinstalled Windows XP about two weeks ago and I am now having some performance issues while playing games. It is not one game in question but all of them. I have to say that these games run smoothly before reinstalling operating system. Do you have some hints about this problem?
Performance issues while gaming can come from different sides. In your case (I assume that hardware is OK and you do not have some overheating problems) I would check my system for spyware and/or viruses. Performance drop can be caused by many processes running in the background and even some antivirus software (most notably Norton and McAfee products) can cause severe slowdowns.