Did you install a software like Alcohol120% or DemonTools or do you use a recent Nero/other CD burning program version? They all can install "virtual" drives where you can mount CD/DVD image files. Get rid of them by unselecting the associated option in these programs.
While the program is still installed, uncheck/deactivate the virtual drives, then uninstall the program. (That means reinstall it, deactivate drives and uninstall again)
Right click "My Computer", click "Properties" and "Device Manager". In the list, click on the plus sign near "CD/DVD drives". Search for something like "Generic DVDROM SCSI CDROM Device" or else that doesn't show name and model of your real DVD/CD-drives. Then right-click these and choose "uninstall".