Special note for both 32-bit and 64-bit versions of Windows Vista, Windows 7

If getting an error when trying to create virtual diskyou need to set the ImDisk driver to auto load.
Easy method:
Right click on command prompt icon and open with administrative privileges, then type or copy/paste following two lines:

sc config imdisk start= auto
net start imdisk

Press 'ENTER' after pasting in EACH line into the command prompt window. This solution should work immediately without reboot. No need to turn off UAC.