So apearson, how bout it? Was the PSU the culprit? If you got the new PSU and it still didn't work, try nihil's suggestion...

I as well reccomend Avast, I install it on every computer I service that's lacking AV software... But I doubt this is the work of a virus...

BTW, nihil suggested that it could be a RAM problem, I'm assuming he got the idea because of the freezing up in windows, if that's the case, then it would be more likely that it's a mobo problem... meaning you have a faulty RAM slot... And the idea of the overclocked video card is a good idea, as alot of them DO come overclocked... and since you've only had it for a couple of months... it kind of makes sense.

Thank you nihil for catching the things I missed, I have a habbit of jumping to conclusions a bit early...