Windows Media Player quit working

Windows Media Player keeps telling me via error message that there is no sound card and/or that the sound card if installed is not working. The thing is I think the sound card must be fine because I can play media via Quicktime and Realplayer. And, I have sound events on my desktop theme. Can it be that WMP just doesn’t ‘see’ the sound card? And if so how can I point the card out to it?