Windows NT has a pretty possiblity of creation persistent SUBST drives, those will not disapper after reboot. In addition, the subst drive letter created with this method becomes available on erly stages of system startup. Thus, services can be started from it. It was quite useful for me when 1 of my HDDs had unxepectedly gone. To avoid registry modifications, re-configuring and reinstalling software, and other unplesant things, the following was done: Data from partitions was placed to separate folders on available disks. Then parsistent substs to these folders were created.

Assume, the backup copy of drive J; is stored in C:\Backup\J folder. We wants system to operate normally until new HDD is installed. For this purpose we need drive letter J: to point to C:\Backup\J folder. This setting must take effect durring boot-time and must be independent on logged in users and their rights. To do this the following steps must be followed:

1. Create String value in [HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\DOS Devices] registry key. Name of this value must correspond to the drive letter being created. In our example, the name of value must be J: to create subst drive J.
2. Set data of the value created to the path to target folder in the following format:
   \??\<path to target folder>
   In our example this will be \??\C:\Backup\J. Note, there must be no '\' character at and of pathname. The only exception is where subst-disk points to root folder of some other volume (e.g J: -> C:). In this case '\' is required.
3. reboot or make the same subst from command prompt:
   subst J: C:\Backup\J

Now (since 2004.02.03) you can use management utility for persistent substs.

REGEDIT4

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\DOS Devices]
"J:"="\\??\\C:\\Backup\\J"