I am working on a system where both of the CD drives do not appear under My Computer. They show in the Device Manager with an explanation point and "Code 39". The usual fix of deleting the UpperFilterCheck and LowerFilterCheck registry entries did not solve the problem or change anything.
I have disconnected each drive and started the computer to be sure that it wasn't a hardward problem with one of the drives. I also tried another ribbon-cable for good measure.
The drives are: Lite-On XJ-HD166S DVD-ROM and Samsung SW-252 CD-RW
System: Dell Dimension 4700
OS: Windows XP Home editon SP3, all critical Windows updates done