It started happening yesterday while I was playing NFSMostWanted on my PC. I was playing, and my monitor just went black and my computer shut down, it was like the power went out. That's what I thought, but I turned it back on, and it worked. But then in shut down again in about 10 mins of starting it up again. I left it off for a while, and grabbed something to eat, I turned it back on and it lasted for about 2 hours then shut down again. I turned it back on later and it worked for the rest of the day. But today it shut down AGAIN. I'm starting to think it's a hardware problem. It usually shuts down if I'm playing a game. I've also noticed Youtube videos framerates are very slow, and the framerate while I'm writing this is also slow. Any help would be very appreciated. Also, could It be dust on the fan? Should I try and clean it?