What does deactivate virual drive

You must have a virtual drive program installed, something like daemon tools or ulltra iso, What these programs do is allow you to open a cd/dvd image on your hard drive without burning it to a disc.

If you deactivate the virtual drive then you will just nedd to reactivate it if you want to mount an image to it.
All it is doing is creating a dummy drive and emulating a real cd drive on your system. Windows and the software you mount to these virtual drives can not tell the difference between virtual and physical drives