pc powers up and goes off immediately

I have a pc with a gigabyte motherboard which has been working ok for
the last 2 years.

Two days ago, it turned off on its own. Since then, when I press the on
switch, it briefly comes on for about 1 second and goes off (lights and
fans come on and go off after 1 second).

What could be wrong? Faulty switch? Power supply finished?
Motherboard/CPU fried?

Nick wrote:
What could be wrong? Faulty switch? Power supply finished?
Motherboard/CPU fried?

Not likely to be a switch problem. PS would be my first guess, followed
by a peripherial card problem, then the MB.

Pull all the cards except the video card and see if you get any messages
from the POST.

Just tried a few things one of which gives a clue.

If I unplug the ATX12v power voltage (I think this goes to the cpu) and
then switch on, the power and fans stay on although the pc does not
boot up for obvious reasons.

So it could be something to do with the cpu (heatsink, fan, power
supply, processor)?

Nick wrote:
Just tried a few things one of which gives a clue.

If I unplug the ATX12v power voltage (I think this goes to the cpu)
and then switch on, the power and fans stay on although the pc does
not boot up for obvious reasons.

So it could be something to do with the cpu (heatsink, fan, power
supply, processor)?

Yes, any of the above...even a shorted capacitor on the MB could cause
this.

Start by substituting a different PS - you can buy one for $20 or so at
newegg.
http://www.newegg.com/Product/Produc...e=&maxPr ice=