Do this before you start hacking in the registry.
A virtual drive should show up under My Computer as another cdrom. Look and see how many cdroms icons you have. If you show more than what you actually have then you have a virtual drive installed. Alot of game copy software install them but don't remove them when the software is uninstalled. You can also look in system properties, hardware (right click on workbench My Computer icon and scroll down to properties and left click, Then click on hardware, device manager, then click on DVD/CD-Rom) and then see if it shows a virtual drive. Also check all the rest of the listings as it may appear under a different heading. You should be able to disable it there it at the bottom of the properties page . On one I had to reinstall the software and then turn off the virtual drives to get rid of them