No sound in Windows 7. Can you help me?

I have a very unusual and rare problem.

1) Windows 7 sound drivers are installed, and installed correctly because I get sound and it says they're installed correctly!
2) Winamp, Media Player Classic, and Windows Media Player 12 all will not play sound from mpg, avi, mp3 (WMP12 corrupts these), and wmv.
3) However, all sound tests play sounds that I can hear. Youtube and other sites with videos I can hear the sound from too.

I am left stumped. Anyone who could figure this out +rep. Seriously, I really have no idea what's going on.

It could be a codec issue, I suppose, though if you're on a fresh install I doubt it.

It could be a codec issue, I suppose, though if you're on a fresh install I doubt it.

Fresh install with K-Lite Codec Pack 4.70 with minor update.

I take it you have the latest (Vista) drivers for your sound card? Try disabling Digital Media Device (found in Sound Devices?) and set your sound card as the default playback device.

I take it you have the latest (Vista) drivers for your sound card? Try disabling Digital Media Device (found in Sound Devices?) and set your sound card as the default playback device.

Yeah, I had the latest Vista drivers.

I looked around and found that Digital Media Device doesn't exist, but I was able to set it as default in the sound options which I hadn't noticed until I was mucking around with the options. Sounds working now, thank you.

EDIT: I need to give other people rep before I can give Chruser Rep, hmm...