Originally posted by Dr Unne
Answer to 90% of Windows questions: Just reboot.
Answer to 10% of Windows Problems:

Upgrade from Windows ME now.

Seriously though, use task manager and close anything that looks like a sound program, it usually works but is not guarrantted. The only other option is in sound properties (multimedia in older version of windows), make sure that the device is not set to Use Preferred Devices only as this sometimes locks up the card if you play some sound.

Only a suggestion though...