Windows 2000 Pro Sound problem

When I play mp3 files, I hear one channel of sound with a hint of the other channel. I have tried Media Player and Sonique players. I have re-installed the OS, the current sound card drivers and current player versions. My original sound card wasa Sound Blaster 128 then I changed to a soundcard with a als4000 chip. No change in symptoms. I can play the files through my network on another PC and the files play correctly. The Sound Blaster card plays perfectly on a system with Windows XP (RC2). I had no problem while using Win98SE.

System is a PIII 600 on and Asus p3v4x mother board. ATI All-in-Wonder PRO 32meg.