Stop that!
I’ve noticed a potential problem with the Mac Pro. Ocassionally the CD-ROM will spin up. There’s no disk in there, but I can hear that high pitch spinning. Usually after I open a directory following a short period of inactivity. I’ve replaced the stock 250GB drive with a 500GB Seagate drive. I don’t think that should cause the CD-ROM access though. Has anyone else experienced this issue?