Okay, new noise from my iMac in the last week or so. Rev B 2.0 G5, 160g HD, only upgrade was some ram from OWC right when I bought it. What I'm hearing is a beep or a chirp. It will last a millisecond if that, sometimes in a pair, usually just once. If I had to place it, I would say left hand side of the machine, if your looking at it from the front. Its in no way consistent, happens at random times. Any thoughts?