Confira a saída do comando mountvol :
VolumeName: Specifies the volume name that is the target of the mount point. The volume name is of the form \?\Volume{GUID}\, where {GUID} is a globally unique identifier (GUID) (for example,
\?\Volume{2eca078d-5cbc-43d3-aff8-7e8511f60d0e}).