Computer Problem (will not start)

Arch Guru XX

Normally I leave my desktop running all the time; I've had very few problems with it. This morning when I woke up it was off, and currently refuses to turn back on. I'm looking for suggestions on why this might be happening as well as possible ways I can diagnose the issue.

The computer is home-built, about 4 years old. All components are from the original build, with the exception of the PSU, which I had to replace about 18 months ago. Computer specs:

CPU: Intel P4 3.0ghz, Northwood core (stock fan)
Mobo: Asus P4C800
RAM: 1 gig corsair (two sticks) - I don't remember the speed off the top of my head
Video Card: ATI Radeon 9800 Pro (128 mb)
Hard Drive: 120gb Seagate, 8mb cache
OS: Windows XP w/ Serive Pack 2

Also has a DVD-ROM and a CD R/W, and a floppy drive. Can't remember the manufacturers at this point.

All of this is plugged into a surge protector.

So here's what's happening: when I turn the PSU switch on the LED on the Mobo lights up as expected. When I hit the power button on the front of my case, nothing happens. No fans spin up, there are no beeps from the case speaker to indicate an error, the HDD activity light does not come on and the front-side case temperature display does not light up. Nothing at all is displayed on the monitor - it doesn't even get to the point where the BIOS comes up. I haven't been able to fine any signs of loose connections inside the case, although I have not had time to do a truly in-depth investigation.

My initial hunch leans toward the PSU, but since the LED on the mobo lights up I know that some power is getting through. Would that happen even if the PSU was otherwise not working? I'm also wondering if there is something wrong with the case wiring, but that wouldn't really explain why the system shut down.

I guess I should note that we moved about two months ago, but the computer hasn't had any issues (until now). Our place is a little hotter so the PC has been running hotter, but not terribly so (idling between 100 degrees F and 108 or thereabouts). I did not see any sign of significant dust build-up in the video card or CPU heatsink.

Any suggestions as to what is going on? I'm at work right now so I can't provide specific details about the components, but I'll try to answer any questions.

Thanks for the help.

Hamju

Power buttons on cases can be finicky and it is possible for them to break. My guess is that the wires are disconnected at the button itself. This happened to my mom's computer recently (her computer would "sometimes" start up, usually when I railed on the button a whole bunch of times) so I had to open up an old case, get the replacement wires out, rip hers out and tape the new ones in. I should've glued them, but didn't have any glue handy. It's not a difficult fix, if you can get your hand on replacement cables.

AtomBomb

You can just bridge the pins on the mobo for a second if you want to see if it's the power button. I used to buy used motherboards as part of my job, and to test them I never bothered to hook up power buttons and whatnot. Just locate the 2 power pins, remove the "faulty" power button connector, get a flathead screwdriver and touch both pins at the same time with the screwdriver. If the power button is faulty, the machine should start up like normal. If it doesn't start, it's not the power button.