Did your PC turn off on it's own - or did you turn it off - and it wouldn't turn back on.
I know this is pretty silly question - but have you checked your power cord / outlet ( tried to plug it into a different outlet if the current one doesn't work ). If you turned your PC off normally - I would be surprised if it just died without warning next time you turned it on.
Last night, I turn off my computer by click shut down button in Window Vista.
Then in this afternoon, I press the power button in front of the case, it wont turn on.
I did try plug it on different outlet, and I did try put a jumper on power switch pins of motherboard, none of them works.
My power supply is Enermax 550W
My motherboard use ATX 24 Pins and ATX 12V 2X4 pins.
My CPU is E8600 overclocked to 4Ghz with a fan.
My Video Card is ATI Radeon HD 4870 2X6 pins with a fan.
My Video Card is overclocked too.
5 case fans. (two in front, one in rear, one on side, one huge in top.)
One DVD and one SATA hard drive.
I just don't know why it there is no power to computer.