computer wont start ATX12V could be problem?

[bot87]

Hi. one day my computer shuts down by itself and wouldnt start back up. I took all the parts off and started connecting stuff 1 by 1. But nothing would start off. Next day, i took out the 4pin main connector(ATX12V) off, the computer started: hard drives ran, the fan on my motherboard spinned, my cd drive ran, but i couldnt see anything on my monitor (everything is connected correctly, monitor works perfectly).

I connected the ATX12V back in, but then nothing would start. So i took the ATX12V back out, and then tried starting it without it again. But this time only the fan runs for 2seconds and then stops. So i unplug and plug my power supply; when i start it this time,(without the ATX12V) harddrive ran, fan on motherboard starts spinning, and cd drive ran. It would be like this most of the time. So im not sure if its the motherboard or not. Ive changed to a different power supply.. but not a new one so not sure if its the power supply either. I had this computer for 2years, worked perfectly. PLease help. :-(

[anrqangel]

Try replacing your psu with a new one, that way you'll know if it's the psu.

It sounds to me like the p4 pin is dead