Lol, I accidently disabled all my drives when using gpedit previously. Sure works a champ!
I just discovered this when checking the registry values covered here:
http://www.pctools.com/guides/registry/detail/148/
You can manually implement this registry edit. It appears the value you would want to enter in hex form would be 32.
You will probably not find the "explorer" key in the HKLM system tree and you would have to add that if you want this change to take place for all user profiles.
To open the registry editor, run
regedit
PS if you haven't created a registry key before, here you would right click on "explorer" in the left pane and select "new > DWord"
Then you name it NoDrives in the right pane, right click on that and select Modify, check "hex" and enter 32