I have close to the same setup. I have never had this problem. XP can sometimes get fussy when you have more than two gigs of ram did you try to run them with only 2 gigs. If that isnt the problem then I would guess it either a heat problem or hardware problem. Sorry I wasnt much help. By the way, vista has gotten a little better since its sp1 has come out. I really dont think xp is that much better than vista anymore. Windows 7 is coming out soon, hehe, so u can just wait for that, i guess.