Running WinXP, Are you experiencing this problem:

If you manually eject a CD-ROM, Windows Explorer still thinks the disk is in the drive. We have searched Microsoft's TechNet as well as many online support lists and have found no definitive answers. So far, we have found that the problem is occurring with some of the Acer 56x and the NEC 56x CD-ROM drives.

If you click on this link you will find a discussion thread at Experts Exchange concerning this issue.