Horrid performance sp3

Apparently I wasnt paying attention and let Sp3 snake its way in. Since then GRID causes my pc to crash. To test it i ran 3dmark06 to make sure it wasnt overheating or a driver problem. It does it with GRID only since the install of SP3. I also noticed my 3dmark06 score was horribly low as well. I scored a 3,500. I did uninstall Sp3 and same results with GRID and 3dmark06. My specs as followed. Am2 6000+, 2gig ddr2 800, 160gig HD, 680watt psu, ATI X1950pro, Windows Xp Home. I was hoping anyone would know a hotfix or if I should just re-install windows. I also know its not the compenents, because I have another machine I tested it in with windows xp and the 3dmark was over 7,000. Any help or positive input would be greatly appreciated thank you.