If you are using Windows Media Player, try updating it, or try downloading WinAmp to see if that works for ya. I would also make sure you have the latest drivers for your soundcard as well. Which ever player you end up using, go to the preferences and make it the default player for that type of file. Sometimes drivers get corrupted by other applications so find one player you like and uninstall the one that doesn't work. Then run disk clean-up and a defrag, it cant hurt.