I had to post that I was having the same problem of the system all of a sudden not recognizing my CD/DVD drive and gettin that yellow "!" in the device manager for it as well.
Many thanks to this website and the posting of the solution. It worked great. I used the CDGONE file link to take care of the problem automatically instead of manually going into the registery myself.
My laptop (for anyone else interested) is a Panasonic Toughbook CF-W5M model operating on Windows XP Home.
Again, thank you SO MUCH!