All iMac optical disc drives are slot-loading drives, meaning that the disc is inserted into a slot that directly feeds into the computer, rather than being placed onto a disc tray that is pulled into the computer. There are several reasons why an iMac slot-loading drive may all of sudden stop reading CDs. Faulty hardware, an unleveled surface, scratches on a disc and a disc that is stuck in the optical drive all may cause a CD drive to stop responding. There are several different troubleshooting techniques that you can do to help you pinpoint the problem and get your iMac back to reading CDs again. Tips Writer Bio
