Hi all, I've got a 20" iMac that I bought about a month and a half ago. Last couple weeks I started noticing a strange "rumbling" noise coming from the DVD drive area. It happens randomly, regardless of whether I'm using the drive or not. For example, it's happening this very moment, but there's nothing in the drive. All I'm doing is some internet browsing. It's a pretty fast rumble - low sounding noise. Now that I think about it, it might actually be coming from a fan... ? Has anyone ever encountered this before? Any ways of finding out what's going on and how to get it to shut up? Thanks!