XPS 420 will not recognize either CD/DVD drives at startup

I have a Dell XPS 420 with two CD/DVD drives.  I recently put in a disk to use and it could not be read on either drive.  I then tried a different disk and had the same response.  I then used Device Driver tosee if there was problem and both drives have the yellow exclmaation point indicating a problem.  When I look at the drive's Properties, I got the following message:

Windows cannot start this hardware device because its configuration information (in the registry) is incomplete or damaged. (Code 19)

I haven't had an occassion to use the CD/DVD drives for about 3 weeks, but they worked fine then.  Something went wrong somewhere in that 3 week period, but I don't know when so I'm not able to use the Restore function to go back to when all was OK.  I don't believe it can be a drive HW problem since it seems to haave effected two separate drives at the same time.

Does anyone have any thoughts of what might have happened and what I can do to try to make work.   I tried telling the drive to upddate the Driver thinking this would install a new driver (or even the old one) and all would be OK, but there was no success.