Hi, recently my pc has had an issue with simply powering on. Im pretty acquainted with pc trouble shooting, ive had numerous pc issues before and have been able to fix each one of them but this one has left me clueless and frustrated. Heres exactly what happens. Once i turn on the mains, and i mean the mains at the wall socket, but pc powers on by itself (i dont even need to press the case buttons). But then it goes off after 3-4 seconds. No beeps , no new hardware installed whatsoever. This has just happened all of a sudden. Once it goes off, however much i jam the case button it simply wont turn on again, but if i turn off the mains and turn it on again, once again it turns on for a few seconds, goes off and the case button doesnt respond at all. Ive tried rewiring and removing and fixing all the ram chips and cards again, but it didnt help. Applied some fresh thermal paste but that didnt work either. Im really helpless on this one, anyone ever experienced this before? Thanks in advance. Heres my spec btw :

Amd 3700+ 64bit
2gb transcend ram
xfx 7600gt
gigabyte mb
2x case coolers
stock heatsink
1x 80gb sata hdd
1x dvd writer
400w psu

I would look at the power supply and the switch on the front of the PC. It's one of those two.

The 3-4 seconds it seems to power on is probably just a normal PSU response to having power supplied to it. The computer isn't really starting up and then shutting off.

Although it's a typical response it doesn't necessarily guarantee the PSU is OK. I know it's not much help but it's probably a motherboard, cpu, or psu problem or a combination of those three.

On your motherboard pull out the wire that goes to your power button(on the motherboard not the button) and try starting the pc by touching the 2 pins with a screwdriver and see if it powers on normal. If it does your power switch is broke and thats a cheap fix. If it still does the same thing then I would try to get another power supply to test with. If this fails then I would think your motherboard is failing.

It sounds to me like in might be a 'short' somewhere. You could start disconnecting stuff (starting with the drives) to see if the system will stay up with each one disconnected.

Hey my computer has the similar problem also, I am still seeking for the reason,some of my friends told me that's the problem of the power supply and some others found that's the problem the cpu fan.

I recently purchased a new case and a psu aswell, but now im having a different issue. MY PC boots, the power led and hdd led light up, disc drive led flashes, but i get no video and no beeps, ive tried using just either one of the two ram sticks, and ive tried onboard video. Nothing worked. My only guess is that my motherboard is probably fried?

Assuming everything is connected right, yeah, motherboard or cpu. A bad PSU, or whatever causes it to go bad, often takes the motherboard and/or cpu with it.