are overridden by the label of the host drive/partition: the custom labels are only used if the host drive has no label. One may then: Delete the host's drive label; Create the proper registry keys for the SUBST drive letter; Create the proper registry keys for the host drive letter (optional, works around the host drive label override caveat); Re-create the SUBST drive to see label changes applied. In addition the LABEL command is able to change the label name LABEL <Your Drive Letter>: "Your label value" Persisting across reboots Drive letters mapped with the command are not available during system startup for services nor do they persist across a reboot. Registry (DOS Devices) The DOS Devices mechanism that underlies subst can be set in registry. This way, the mapped drives are usable immediately during startup. Create a new registry entry "String Value" in the following key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\DOS Devices The name should be "X:" where X is the drive letter. The value should be the path in one of the following NT Object Manager forms: \??\C:\some\directory (preferred) \DosDevices\C:\some\directory (long version of the former) \Device\Mup\127.0.0.1\C$\some\directory (discouraged, as this goes through SMB share) There are tools available to make the necessary changes for the user, including . The relative to this thematic registry key is HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices. It defines mapping of drive letters into particular hard disk partitions, similar to /etc/fstab on a Unix system. It also can be edited manually, but only at that time while that particular installed Window operation system is "inactive". So that, for example, if you currently boot from "D:\Windows" then you can edit the HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices key of Windows that is installed in a "C:\Windows" folder, for an instance by doing the following actions: run command: reg load hklm\$system C:\WINDOWS\system32\config\system run command: regedit.exe edit registry key HKEY_LOCAL_MACHINE\$system\MountedDevices (that represents the HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices registry key of the Windows instance that is installed in C:\WINDOWS) close regedit.exe run command: reg unload hklm\$system (to complete the editing procedure) Importing reg file The easiest way to do this is to create a registry file (.reg), and double click the file to import the settings into the registry. Here is an example registry file. REGEDIT4 [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\DOS Devices] "F:"="\\??\\D:\\Mount\\db" "G:"="\\??\\D:\\Mount\\log" After configuring the registry the computer must be rebooted for the changes to take effect. Run on boot (batch) Create a batch file to run the built-in SUBST command to create a virtual