- You can NOT add the special group "Virtual Machines" through the GUI (that I could find), you must use the icacls command:
icacls "C:\Users\Public\Documents\Hyper-V\Virtual Hard Disks\MountPointHere" /grant "NT VIRTUAL MACHINE\Virtual Machines":F /T
Successfully processed 2 files; Failed processing 0 files
The "/T" switch will propogate permissions to files/sub-directories under the root of that volume.
Bravo :-)