hrmm.. could be a number of things.. maybe a bad power supply, bad video card.. try booting into safemode and see if it still does it, if not, then its a driver issue, if so, then its a hardware issue..
to boot into safe mode, you hit the F8 key after the POST, before the windows splash screen..
to boot into safe mode, you hit the F8 key after the POST, before the windows splash screen..