Sound problems with XP

[El Psycho Diablo]

This isn't a critical problem of any sorts, but it's annoying as hell. While playing a game designed for Win 95/98 like Fallout 2 or System Shock 2 (Both games I've had trouble installing in the past) the music will be just fine, but the sounds (gunfire, speech, etc) won't work.

 

Setting it to Win 95 or 98 compatibility mode works for a few minutes, but then after a minute or two, the sound will dissapear again.

 

Anyone know how to fix this?