'No playback device'-- but there one!

The sound on my computer stopped working a few days ago--
booted up the computer one day, some crap got corrupted
(but fixed) and I've finally decided to do something about it.

I know the speakers work; I've tested them with my CD
player. The driver for the sound card is still there, and I
have actually re-installed it. But for some reason, my
computer doesn't seem to realize all that. It still says
that there is no playback device, and when I go into
Control Panel/ Multimedia/ Audio, all the controls are
greyed out and I can't do a darn thing. The sound card is
listed under System/ Device Manager, but not where it
matters the most.

How can I get the sound working again?