I have given more details of the problem at https://answers.launchpad.net/ubuntu/+question/81027
Basically, I have two drives: a CD-RW and a DVD player. Every thing worked in Dapper, but when I upgraded to 8.04, the DVD drive disappeared. Now I am updated to Jaunty and I still can't find the drive.
However, if I put an system install CD in the DVD drive, it recognizes it and begins to install it. So there must be a driver somewhere.
Thanks for any help.