The Windows Subst command is used to create a virtual drive.
Virtual drives are in essence a root alias to a much deeper folder path. They are very useful for software testing, or the like, where one may want to simulate the root of a hard drive partition without actually creating a partition.
These virtual drives are not junction points, nor are they mapped network drives. Virtual drives function nearly the same as a mapped network drive, although they will not appear on the list of drives under the Net Use command. They may be assigned to: a local path, a path on a removable storage media, or a network path (on a mapped drive or a UNC path). Whichever type of path a virtual drive is assigned (hard disk drive, network, removable storage) path, it will appear in My Computer under that type of drive. Virtual drives assigned by the Subst command do not live past the current Windows user logging out.
The output of a net use command will not display a virtual drive. However, the output of fsutil fsinfo drivetype and fsutil fsinfo drives will list information about virtual drives as if they were real drives.
Below is a snippet of one my issues, that I'm still in the process of editing for the BBT list:
The DOpus Raw command: "Clipboard COPYNAMES=unc" will not work when a shared network drive has been assigned a drive letter using the SUBST command, rather than using the Net Use command (or Map Network drive). The command: "Clipboard COPYNAMES=unc" works well for mapped network drives, and when listing a UNC path. However, a network drive could be assigned a letter via the SUBST command rather than mapped via the NET USE command (Type "SUBST /?" at the Windows XP Command Prompt for more information.
The above behavior seems to suggest that Opus treats all virtual drives as local drives, not network drives.