dvd readers with exclamation marks

Under xp pro - sp3, the two optical disks suddenly became unavailable on a friend's pc. They are recognized by the system but both have an exclamation mark in the the Device Manager.

There is no virus (checked that). I intend to do the following:

1. uninstall the devices and reboot

2. If that doesn't work, I'll try a repair-install.

Is there anything else I can try?