Computer powers on, then immediately powers off

[JimRune]

So, I've replaced the motherboard, CPU, and RAM in my computer. I've kept everything else the same: hard drive, PSU, video card, disc drives, etc. When I turn on the computer with everything plugged in, it all powers up, however the screen stays blank and the two DVD drives I have begin to make clicking noises. The lights on these drives stay lit and after about 5 seconds the computer powers down completely. When I remove everything and only have plugged in the hard drive, video card, and mobo, the computer powers down at about 3 seconds after the button is pressed. Here are my specs:

520W PSU
AMD 6000+
7800GT video card

The hard drive is the same one from my old computer, I was planning to format it once I got the computer up and running. Now, since my old Windows install is on that drive, could that be the reason why this is not booting up? It doesn't seem likely, but I'm throwing that out there anyway.

[RamonGTP]

Sounds like a bad power supply to me. An existing installation on the drive should not cause the computer to shut down, and existing and incompatible installation usually results in the computer locking up when windows loads or the PC going into a reboot loop. You can very easily rule out the hard drive by simply disconnecting it and leaving ONLY 1 stick of ram, the processor and video card.

Also, make sure the bios reset jumper on the board is in the correct position and not in the reset position. I've come across a few boards where the jumper was on the wrong pins and the PC would not boot.

[JimRune]

There are no jumpers set or no incorrect jumpers set, I have tried booting the computer just now, several times, with only 1 stick of RAM, the CPU installed and CPU fan installed, and the PSU plugged in. It still immediately powers down. I removed the motherboard from the case and placed it on the anti-static bag it came with, hooked it up basic again like I described before, tried again and still the same result, which rules out a grounding problem. Is there any way to test it's my PSU? Before when I was having trouble, I checked all the voltages via multimeter on my PSU and they were fine.. That was only a few days, maybe a week ago. I find it odd it would just stop working like this now after I put new parts in.

[RamonGTP]

Voltages don't tell nearly the whole story. First and foremost, the voltage testing would need to be done under load, but even that's not enough. It is entirly possible that the voltages can look stable on a multimeter, but the current may have a lot of "noise" which a multimeter cannot pick up. The only definative test of the PSU is to simply try a different one.

[JimRune]

Alright. I will head out to a computer shop today and pick up a good power supply to try it out. Thanks much. I hope this works.

[JimRune]

Sigh. Bought a new power supply, same exact thing. Computer starts up, then goes right off again. This doesn't make any sense. I have replaced EVERY single vital part of this computer, there is no reason for it to be doing this. This is absolutely insane. I don't know where to go from here.

[electric]

double check the heatsink is install correctly [ manual ]

the bios may be shutting the computer down because of a
high heat temperature there by protecting the CPU

[JimRune]

Um, something weird just happened. When I went to pull the heatsink off the CPU, it pulled the CPU right out of its socket. The stock thermal grease that came with this thing has glued the CPU right to the heatsink. I'm so confused. What's going on and what do I do? The pins are all fine, nothing was damaged or bent when I pulled them all out.

[electric]

maybe you forgot to lock the CPU to the motherboard


http://cr.yp.to/hardware/assembly.html

[JimRune]

No that's the thing, the little lever that locks the CPU in place was down and in place. :???: I can't get the CPU off the heatsink now...