Question : Problem: Computer powers on and then turns off

Different pc. Different problems. Lord.

This time I'm dealing with an AMD quad core processor and an ASUS motherboard. The computer turns off, fan spins, etc then the whole machine turns off after about 2-3 seconds and boots back up. Does the same thing. Rinse, lather, repeat. No bios, no video, but then again it's not booting past  2 seconds so that would be understandable.

The thermal paste provided with the processor/heatsink from newegg is a rather thin layer, and originally the heatsink came pre-pasted and I simply stuck it on the processor and clamped it down and all that good stuff. I don't know if its the paste for sure, but looking at other threads on the internet this 2-3 second boot on, boot off deal is a characteristic of (but not limited to) improper or excess thermal paste. I don't have any current, and as it's Christmas, nothing is open to where I could even get some.

Two questions:

A) STRICTLY for the sake of booting and seeing a BIOS screen (not long term applying to the heatsink and clamping on), can I use some kind of substitute either exclusively on the processor with no heat sink or heat sink + processor to test to see if it'll even go into BIOS?

B) Could it be something else entirely? The mobo has onboard video, onboard sound, onboard lan. There are no other cards plugged in except for an IDE to SATA converter card for my IDE HD.

-Travis

Answer : Problem: Computer powers on and then turns off

>> What do you mean any earthing going on? How would I be able to tell? The mobo stands are the riser screws right?

Correct.  Mind couldn't find right words.

Remove motherboard from case and place on piece of cardboard.  This will stop it touching the case.  Reconnect power supply and power switch.  See if problem still occurs.

If it does you've isolated the problem to either power supply or motherboard.

Oh, and silly question.  The auxillary power supply cable is connected to motherboard isn't it?