Computer shuts down after 1 sec with one PSU, but not other PSU

The power supply in my computer recently died and I ordered a Thermaltake TR2 600W to replace it. When I plug the power supply in, the power supply and cpu fans spin for about a second then everything shuts off. I've plugged the power supply into another computer, and everything works fine, with 2 hard drives, CD and nvidia 7900GTO video card plugged in. I tried the cheap 20$ no-name 450w power supply from that computer into mine and everything works fine, with 2 hard drives, 2 CD and a nvidia 8800GS video card plugged in. I stripped all possible components from this computer to only a single HD (the motherboard has an on-board video) and the Thermaltake power supply still only powers for about 1 second before sutting down. All tests were conducted from the same wall electrical outlet. Do you have any idea what might be causing this, why is the power supply working fine in one computer that requires a decent power load while nothing happens in the other computer even when the load is lightened to the max? Does the thermaltake power supply read error codes from the motherboard or some such and shut down while the cheap power supply just dumbly supply power?

Thanks!
 
Have you attached the axillary 12 volt connector from the Thermaltake to the motherboard near the CPU?
 
Indeed everything was plugged in.

I since managed to make it work. I plugged in the HD from another computer to the Motherboard that wouldn't start, it gave me a blue screen of death, but when I re-plugged it's original HD ( the one whith which the power would only come on for a second) it booted fine and ran for hours.

It seems as though there was an error code on the motherboard which required a successful bootup to be cleared to allow the thermaltake PSU to power-up.

I re-plugged all the hardware and it ran for approx 24h before shutting down. So I unplugged everything but the video card and the main HD, and now it's ran without a hitch for 3-4 days non-stop. I'll replug the rest of the hardware one by one to track down the defective one, but it seems to be either the secondary HD (which is 2-3 years older than the main) or the DVD-RW or DVD drve.

Thanks
 
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