Could be software or hardware. I have Vista (on an HP btw) as well as on a super-duper self made mega gaming machine. No problems on either. My first reaction is always memory - Anyway you can work on only half and then see if the problem still occurs? If it does swap the half still in for the removed half and try again. If you still get no joy try upgrading your firmware. Last shot beofre giving in to the 'pros' - try one of the many system checkers that you see advertised when browsing the web. Steer away from Symantec and the big boys and you should find something either free to try or pretty cheap. CHECK INDEPENDANT REVIEWS FIRST! and back up your system of course, but you would always do that wouldn't you? :-)

Cheers

DeG