Old PC won't turn on anymore. (ASUS P4P800 Deluxe)

[NizyBoxer03]

Hello. I'm trying to fix an old pc.

The pc booted up normally the first time I powered it on: Boot, Bios POST, loaded Windows 7.I moved the mouse around, it worked fine. I tried to open the Start menu, and it froze. I couldn't turn it off by holding the Power Button, so i unplugged it.

I tried to turn it on again. It froze at the Windows 7 loading screen. Again, i couldn't turn it off, so i unplugged it.

I tried to turn it on a third time. No Bios POST, stuck in a peach-colored screen. I had to unplug it again.

But when i tried to turn it on a fourth time, it powered on, the fans started spinning, and then it powered off. This keeps happening every time I try to turn it on.

When it worked, the pc would beep (Bios POST) when powered on.

I tried removing every component, including RAM sticks, and videocard in the hope it would beep an error code, but nothing happens.

Here's an observation i made:

When nothing is plugged into the motherboard (except for the fans), it powers on, but it doesn't do anything else, and i have to unplug it to turn it off.

When the CPU power cable is plugged into the motherboard, is powers on, but then powers off inmediatly.

The motherboard is an ASUS P4P800 Deluxe

Is there a way to make it work again?

Any help would be appreciated a lot.
Thanks in advance.

 

[Tradesman1]

Tried a different PSU? Have you benched it to eliminate the possibility of a short? Have a guide that might help here:

http://www.tomshardware.co.uk/faq/id-1753671/bench-troubleshooting.html