it is a software problem. your need to update your device drivers for the sound card first. this will be at the vendor's web site. if that doesn't work, then you need to see if other applications can play sound when Media Player has problems. run some other program that plays sound like QuickTime and see what happens.
Herb...
WindowsXP,
I get a message that the hardware is not responding or that another application is already using the sound.
Windows Media Player error: Error ID = 0x80040256, Remedy ID = 0x00000000.
Do you think I need to change the sound card, or is it a software problem?
I tried to trace the hardware but it seems to be working fine (as far as I know).
Any suggestions please.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic