Audio problem with Windows XP

I currently have a problem with Windows XP when I try to play any music or video. I have a Dell Dimension 8200, 1.8 GHz with integrated audio. When I put a music CD or DVD in, the voices are drowned out by the music, and what I can hear of the voices sounds hollow or ?in a can? like. This occurs in both Windows Media Player and RealPlayer. It is not the speakers, I have run a system diagnostic on the motherboard, pulled each of the expansion cards out, and none of this changes the problem and Dell is at a loss and wants me reload everything. Any help would be appreciated. Thank you.