PC turns off randomly

[Uncle Rico]

I'm having a problem with my new build, it keeps turning itself off at random times without warning. There's no specific pattern that I have noticed. Sometimes it won't even stay on long enough for me to reach the bios, and other times it will go all the way into windows and stay on for a while. The first time I boot it up it was on for a good 4 hours, then it shut off. Turned it back on and it stayed on for like 2 hours. Now I'm at a point where its turning off at random times. What could be the problem?

==>EVGA LGA 775 NVIDIA nForce 750i FTW SLI ATX
==>Intel Core 2 Quad Q6600 Kentsfield 2.4GHz
==>EVGA GeForce 8800GT 512MB
==>mushkin 4GB (2 x 2GB) 240-Pin DDR2 1066 (PC2 8500)
==>Western Digital 500GB 7200 RPM
==>LOGISYS 650W

[not important]

Have you checked your CPU temps for overheating? Never heard of LOGISYS PSU...did it come with a case?
Are you seeing a Blue Screen before it shuts down or does it actually power off?

[mattaggie]

I had this same problem about a year ago. The culprit was the keyboard, I built a new PC and used the same keyboard only to find the same problem was happening. So try a different keyboard and see if that helps.

[rapidarp]

I had an old eMachine back in the day that did this for a while. I'd wake up in the morning and the system would be on. I installed a new power supply and the problem was solved.

[peter8d9]

So what should the corrective action be if its a blue screen?

[Uncle Rico]

I downloaded speedfan and it shows the cpu temps at around 45C. Its also showing the system temp at 84C. Could that be right?