The command to remove a drive letter - which shouldn't be needed, but hey, Win10, there are still some bugs - is mountvol <drive> /D
, so for you it would be mountvol S: /D
and mountvol T: /D
. You can also try mountvol /R
, which should remove all drive letter assignments for which there is no currently mounted drive. You can also try using /P
in place of /D
, but it's intended to be used while the volume is actually present.
You can also use the remove
command in diskpart
to remove drive letter assignments. You mentioned using mountvol to try re-assigning the drive letters but didn't mention trying to remove them. I'm pretty sure it just calls the same APIs as mountvol
, actually.
All of these commands will need to be run as Administrator, naturally.