PC turns off, then turns on then turns off... etc

[Mediator14]

I built my brothers computer 3 or 4 months ago and it was working perfectly until now. It is water cooled, quad core, 4 gigs of ram, single HDD. I have built numerous computers in the past and never had a problme quite like this... After turning on the computer it turns itself off after about 2 seconds, then turns back on and the cycle repeats infinitly. I dont think anything internal was tampered with from when I built it but I cant think of anything thats not a hardware issue that would cause this. It never even makes it to the bios. Suggestions?

 

[Shadow703793]

Clear CMOS (remove battery).

 

[Mediator14]

I had tried that already... Its cool now though I fixed it. 1 stick of ram was bad. Pulled it out and it booted right up.