PC turns off after several seconds

[verbality]

Hey,

My pc started to turn off after about 2 minutes. Then after 10 seconds, followed by 2 seconds. I figured it was the power supply so I bought a new one. My old one was 600 watts so I bought another 600 watt power supply. It turned out I even bought the same brand, OCZ Technology.
With the new power supply my pc won't even turn on. A couple lights light up on the mother board just like with the old power supply, but my machine won't power on. So I plugged my old power supply back in and it did the same thing as before. My pc would stay on for a couple minutes and shut down and then go down to staying on for a few seconds.
So what's wrong? Are not all power supplies for all pcs? Can it be that the new one isn't compatible? I understand there's always a chance that it was just broken out of the box.

- Intel Core 2 Quad Q6600 2.4 ghz OEM
- 4 Gigs of ddr2 ram, 4 sticks of 1 gig each
- XFX nForce 680i LT SLI motherboard
- PCI Express x16 graphics card
- one sata harddrive, 450 gigs
- one 500 gig harddrive (not sure what kind it is. it was external but the casing's power broke so I stuck it in like 3 months ago)
- one dvd dl drive (plan to get another)
- 2 12mm fans, and 2 8mm fans in case

 

[Onus]

Check the CPU HSF; is it [still] properly mounted, or has it come loose? Shutoffs in a decreasing period of time are often due to overheating.

 

[verbality]

I did run it with the case open and watched all the fans working (until it all shut down). I wouldn't be surprised if It's the heat sink fan because I remember it was kinda cheap. Like $25 and has always been very loud.
In case I need a new heat sink fan, does anyone have any recommendations that I could go out and get, say at Micro Center?

 

[verbality]

I bought a new power supply and it all worked out. Turns out the old one was done and the first new one was defective.

Thanks

 

[Onus]

All's well that ends well. Perhaps it was the PSU that was overheating.

 

[verbality]

Best answer selected by verbality.

 

[Onus]

Thanks. Hopefully your PC will run well. Continue to monitor your temps just in case.