Computer shuts off after about 30 seconds...

IT WORKS! But it only stays on for about 20-30 seconds before shutting itself off. Help? My first guess was that the CPU is overheating, but would it really overheat that fast?

Specs:

PSU: Aspire ATX-AS520W 12V

Processor: IntelCoreDuoE6600

Graphics card: 8800 GTS 640 MB Superclocked

RAM: 2GB OCZ DDR2

Motherboard: ASUS P5NSLI

Computer shuts off after about 30 seconds...
If it wont power up and everything is properly connected then its surely the power supply...Id check all connections again then if its not working get the PSU replacedComputer shuts off after about 30 seconds...
Alright, that's what I was guessing I would have to do anyway. Thanks.
The hard part about this problem is that it could be anything from RAM issues to CPU. Its most likly the PSU. If you have an extra PSU hook that one up and that will tell you.
PSU fans or lights don't work till it is connected to the motherboard which in turn is connected to the front case power buttons. After that if you power it up via the front case power button it will light up and the fan will turn on unless it's defective. Apsire isn't the best PSU, but they aren't horrendous either.
Power supply now works fine. Computer runs, but now I have a new problem which I just added as an edit to my first post...help please :-)
Does it beep or anything when it shut off?



If the CPU heatsink isn't applied properly, what you're describing is pretty much how it would act... it would turn on and run normally, while the CPU temp skyrockets. When it hits thermal protection, the entire comp will just automatically shut off.



You could try getting into the BIOS and looking for the CPU temps there to see if they're climbing. It's not the best thing for your CPU to let it do that over and over, though. :D
I *was* having problems applying the heatsink during construction...I would turn all the pins and it would just fall off anyway. It finally stays on now but I'll check it, thanks.

Oh, and I'm not sure if it is a beep, but there is definitely a noise when it shuts off. Kind of ''click'' like.

Heatsinks not on correctly.
THANKS! I'm now installing Vista as we speak. Wooohoooo!