Using Windows Seven SP1 x64.
Start "7zFM" for windows 32 bit version 18.06 or 64 bit v 21.00 alpha
Use the "Folder up" button all the way back until "\." is displayed in the list.
Double-click the "\." entry.
Double -click any of the volume letters listed.
See "Access is denied" error message.
Go back to "Computers", select it and then select a volume letter with success.
That formatted well! For some reason the double back-slash turned into a single backslash
It should read "\\."
It's low level access to volumes data that requires Administrator rights.