Justin from Pittsburgh, Pennsylvania loves his DOS games. He wanted to know why XP wasn't playing sound from them. If anyone remembers, DOS pushed sound directly to the hardware. You needed to set your IRQ ports and DMA channels properly before the software would “do” anything.
With the introduction of 2000 (XP's predecessor), it was no longer possible to send sound directly to your hardware. The sound must now pass through a DirectX layer before you'll be able to hear anything coming from those old DOS apps. To do this, you'll need to download a little program called SoundFX 2000.