Stupid computer!

[etoven]

True, but honestly I don't think a bad sound card would prevent the system from even powering up.

The big 3 for something like that is: motherboard, power supply, and CPU. Modern computers will at least give an error beep if the RAM is no good. If you can double check those things, then that should solve the issue. I guess I should ask how far the startup process normally goes when it fails to startup. Does it fail to power up entirely?

In my A+ training class we troubled shooted problems including PCI cards causing computers not to boot up. When the computers starts up the first thing it does, even before the monitor is given power is it runs a process called POST (Power On Self Test) Which is basically a hardware diagnostic, if a PCI card fails post, the monitor will remain blank and the system enters a halt mode. Exactly as Black Falcon describes. It's also noteworthy ABF that a loose PCI, or PCI express card can cause a POST failure. You did say that when you remove the sound card you dont have a issue? Try removing the sound card, and both blowing out your expansion slot, and then cleaning the terminals on your expansion card. Finally reseat the card in the expansion shot, making sure that the screw that holds the card in the bay is good and tight, and that card is all the way in the slot.


Finally if that doesn't work, you may have a issue where the computer has suddenly decided to assign the card a bad IRQ which can also cause a POST failure, moving the card to a different slot usually fixes this problem.

EDIT:
This also might be helpful...
The Comptea process for trouble shooting POST problems:

I know it's a pain in the ass, but it's guaranteed to track down the issue.

Disconnect all drives and remove all PCI cards. Next remove the RAM from the computer. Install one stick of RAM and power on the computer. If that works, install another stick and so on. If all the ram sticks check out, next start adding expansion cards to the system one at a time testing a power on. Finally add the drives back one at a time until the problem is reproduced. Soon you will discover your culprit.