Wheres the sound gone?

[raceboy]

Pooter numpty here so go easy
When I click on any of my audio MP3 files Windows Media Player opens up and tells me this.........

windows media player said:

Windows Media Player cannot play the file because there is a problem with your sound device. There may not be a sound device installed on your computer, it may be in use by another program, or it may not be functioning properly.

It worked fine last time I used it what's gone wrong
The speakers are still plugged in and turned on I'm not that much of a numpty