Sudden Power Loss!!

I have not used my comp in a month or so. I just hooked things back up yesterday and it originally had trouble stayin on. Eventually after a few cold boots, it stayed on and I played some games. Then after I tried to exit a game, poof it just shutdown. Now, even if I unplug everything only the power light comes on (most times) and the fans wur. For some reason I did get the cpu running once, unknown reasons why, when tested it with other power source for the first time, but now again it doesn’t even boot. Just turns on the fans. 🙁 I’m very novice at IT stuff, and it’s a pretty new power supply as well.