Computer Doesn't Turn On

[amit]

Hi Guys,
I have a strange problem with my computer.
It works fine but after a few hours of regular work, the computer shuts down:
The front lights (power and hd) are working, and I can hear the fans turning but the screen turns dark and the computer doesn't respond to any action I do. I try Ctrl+Alt+Del, I press the Reset and Power buttons but nothing helps.
The only thing I can do to turn it off is unplug it from the wall.
When I plug it back, The screen is still dark and the computer doen't respond.

Only after some frustrating hours , the computer returns to its senses and responds to the power button.

These problem started a week ago, but I don't remmember any special changes I have done to the hardware or software.

My system is:

1. CPU : Pentium 4 - 3 Giga, and 800 Mega Hz Bus.
2. Mother Board : Asus P4P800
3. Memmory : 1 Giga (passed MemTest).
4. VideoCard : fx5900 Ultra.
5. Psu : Antec 430 Watt.
6. I have installed a Cooling system for the CPU.
7. UPS
8. Windows XP Pro.
9. Zone Alarm FireWall and Avast Anti Virus.

I can't turn on the computer even if I try the following :
1. switch Video Card.
2. unplug HardDisks (The computer doesn't turn on)
3. bypass the UPS.

I appriciate any kind of help because as you can imagine it is a very annoying problem.
Thanks
Amit

[Yuanji]

antec has been having some problems with thier PSUs. might wanna check it out.

[Cricket]

Does the fan in the power supply spin when your computer is running okay? If it doesn't, that would cause the power supply to overheat and shutdown.

Cricket

[amit]

Thanks guys for the reply:
The psu's fan is working fine. But just to be sure, I am now chaning the psu. And I will wait to see if the computer crahses with the new psu.

[Yuanji]

if that doesn't work, try taking off your side panel, and blow a fan onto your comp and see if it's a temp problem.