Yesterday afternoon, my computer shut off just minutes after turning it on. I could not get it to power on after that. I've had it for a mere two weeks now, and this is the first time it's happened. I replaced the power supply today and got the same issue - I press the power switch, my fan LEDs come on for a split second, then nothing.

Then I did some tests. I removed any internal cards and fiddled around with everything to see if I could pinpoint the issue. I arrived at an odd conclusion: when I unplug the PSU's 4-pin motherboard connector (shaped like a square), the PC will turn on. But then I get the problem of not having video.

So, I can get it to power up now, but can't get the display working. My video card works fine - a 7800 GTX I got yesterday, and I tested it on another system. I have tried three different monitors to see if that was the issue, too.

Please, any help is appreciated. I just don't know what to do here.

System specs:
XION II case
450W Antec Power Supply
2GB Corsair ValueRAM
nVidia GeForce 7800 GTX

Could something have have gone bad in the PSU?

Try the PSU in another computer or, if you have one, try a different PSU.

Sounds like a bad MOBO to me.

best of luck Frank :

Try it without the video card but with the 4 pin connector. If it fails like that, I would suspect the motherboard.

I've tried absolutely everything now. I replaced the power supply. I replaced the RAM. I replaced motherboard. I even replaced the processor. I tested the monitor and video card on other machines an they run fine. I tried different IDE cables and separate hard drives. I am utterly stumped. Please, please help me!

*cries*