I'm not positive but it sounds like you might have a sound card problem. Do you by chance have a SoundBlaster PCI card?
If so, you might want to make sure that it's in a PCI slot that doesn't share IRQs with other slots or onboard devices.
Each motherboard is different but usually, slot 2 and/or slot 3 are pretty safe bets. Though on a system I just set up, slot 4 was the one that didn't share. You should almost always avoid slot 1 (the one closest to the AGP slot).
Also, for SoundBlaster cards, make sure that you have the latest drivers installed.
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Krick