While playing games, not while doing anything other than that, my computer will shut down and I will have to turn it back on. I dont think its an overheating issue as I purchased a new VERY powerful fan, its cooled my computer almost 20 degrees. When runing games for a while, the hottest my gpu gets is 57 and my cpu gets maybe 50 at most. Another fan is on the way too. My friend said it may be a faulty power supply so Id like input before I replace it.
I have been having that problem and from my experience and also advice that people have given me, it seems to come from a faulty power supply most of the time. I believe that your brand is a budget brand and the power rating it says should be taken for a grain of salt. You probably need to invest in a name brand power supply like Antec or Corsair.
Well first be sure thats what it is, would be nice to have a second opinion as I haven't built a PC in at least a few years. I am planning a new build in the next couple weeks that would probably have about the same power consumption as yours (Phenom II x4 970, 470GTX Super Overclock) or possibly a little more, and I singled out the Antec Earthwatts 750 which had a good price drop at newegg at the moment.
And just fyi, the reviews on your current power supply are... less than stellar to say the least. I can't guarantee that is your problem but it does sound extremely likely. Might in a rare case be a bad RAM chip, but my experience with that is it doesnt generally shut down, it blue screens. And it would probably do it at some point outside of gaming.