Originally Posted by subway1234
I was working on my computer when the monitor suddenly went black.
We see the problem a lot... almost always the problem is a bad/blown power supply. Smaller shops may be more willing to do extensive testing for you. A power supply can be shot and still supply power to the PC, so you might see fans spinning and no video because you're not getting correct voltage.
Another thing you should check is to make sure expansion cards and RAM are correctly seated. Since you said the system was working one day and not the next this isn't likely the problem.
A sure sign of a bad motherboard are popped capacitors. See here: http://www.jebswebsite.com/misc_pics...capacitors.jpg
It's not likely that most shops will solder new capacitors on a motherboard for you (we do if it's machines we've built, but we're a not for profit and our volunteers do it because they love to solder). If you board does have bad caps it would probably cost you more to have the caps replaced than the board is worth...
My advice is to get your PSU (power supply unit) checked out first, and check to make sure everything is seated correctly.