Unfortunately your earlier answer has ruled out most of the obvious solutions.
The next thing I would try is uninstalling the driver for the cd drive.
Click Start, click Run, type devmgmt.msc
Expand the DVD/CD-ROM drives tab
Click the cd drive that uses the driver that you want to remove (if you have multiple cd drives it won't hurt to remove all of them).
On the Action menu, click Uninstall.
When you are prompted to confirm the removal, click OK.
Restart the computer it will identify the drive & install a new copy of the driver.
It may also be worth verifying that no system files have become corrupted.
Click Start, click Run, type:
sfc /scannow
The system file checker will go through all the system files & if it finds any have been damaged it will replace them automatically.
For what it's worth microsofts help page for this issue is here:
http://support.microsoft.com/default.aspx?scid=kb;en-us;324129&Product=winxp