I put together a computer for my brother recently and it has a strange audio problem.
Whenever you have music playing (like an mp3) and launch something for the first time (like when something loads into memory for the first time since the last restart) it gets Matrix-style lag/distortion. I have a clip of it that I took with my mp3 player that you can listen to
here (there's a lot near the end of the clip).
I thought it was the on-board sound that was to blame but the addition of a PCI sound card didn't solve anything.
What could be causing this?