This is probably because subst
creates only transient mappings, i.e. the mapping will not last over reboots. You can add permanent mappings in the registry key Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\DOS Devices
with drive as name (e.g. X:
) and the folder as value, prefixed by \??\
(e.g. \\??\C:\\some\folder
). The setting is active after a reboot. You can then share this new drive. For later reference, you can also put this into a .reg file and open it:
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\DOS Devices]
"X:"="\\??\\C:\\some\\folder"
This is nicely explained e.g. in the wikipedia SUBST article.
But are you really sure your software insists on the share covering a whole drive? Clients usually don't see or care about the real path on the server. If you want to run the software on the server and it complains there about not having a whole drive, you can also map your share to a drive and run it from there.