I suggest to use specific tools on win32 systems:

discupulus@:D>perl -MWin32API::File -E "say for Win32API::File::getLog
+icalDrives"

C:\
D:\
F:\
L:\
M:\
[download]

Or I'd go for some system calls brutally parsing it's output (maybe after this, also -e results):

# admin privileges not required: all drives included network ones:
discipulus@:D> fsutil fsinfo drives

Unità: C:\ D:\ F:\ L:\ M:\

# admin privileges not required: only network ones:
discipulus@:D> net use

Le nuove connessioni non saranno memorizzate.


Stato       Locale     Remota                    Rete

----------------------------------------------------------------------
+---------
             L:        \\bip\root\work\discipulus   Microsoft Windows 
+Network
             M:        \\bip\ROOT\DATA    Microsoft Windows Network
Esecuzione comando riuscita.

# admin required: only logical disks
C:\WINDOWS\system32> wmic logicaldisk get name

Name
C:
D:
F:
[download]

L*