Because I've discovered that my NewToMe/used powerbook's combo drive won't read cd-rs. But it will read pressed cds/dvds and dvd-rs. So I ran the AHT and it doesn't acknowledge the combo drive's existence. (Ran the AHT after repairing permissions, fsck, PRAM.) This is only my second mac and I never had any problems out of the ibook, so I've never seen the AHT screen until now and don't know if it tests the optical. 12"pb 1ghz 1.25mb 40gb hd combo drive AE and Bluetooth Edit: And I'm relatively certain that the problem isn't the OS - it can read the same cd-rs when using a dvd-burner in a firewire enclosure.