I picked up another CC and not feeling like doing any real upgrading right now, I just dropped a LC550 motheboard into it. On restarting it I noticed ther was no startup boing an in fact no sound at all. With the original CC motherboard ther is in fact sound. I then tried another LC550 and two LC520 motherbords and I have no sound with them either. Trying them in another CC fails to produce sound too even though it too works with a CC or LC575 motherboard. I don't recall reading anything about the lack of sound anywhere.