Question: What I'm looking for (and not sure if it's possible) is that we have 16 mapped network drives that are mapped when any user logs on, what I would like is to cut this down to just one visible drive yet leaving the other ones still usable to certain programs. I would just un-map them, however one of our constantly used programs writes to almost all of the drive letters so they need to be mapped for just that program, however they do not need to be visible to the user. Is this possible?

Answer: 
This can be done with group-policy ([doc](http://support.microsoft.com/kb/231289)). It hides the drives in Windows Explorer, but the drives are still accessible through other means, such as the command-line or API calls from programs.
[Defining Local and Remote Drive Visibility Under Windows NT 4.0 or Windows 2000](http://support.microsoft.com/?id=158457)

> 
> The NODRIVES entry (reg\_dword) located in 
>  **HKEY\_CURRENT\_USER\Software\Microsoft\Windows\CurrentVersion\Policies \Explorer**
> 
> 
> uses a 32-bit word to define local and network drive visibility for
>  each logical drive in the computer. 
> 
> 
> The lower 26 bits of the 32-bit word correspond to drive letters A
>  through Z. Drives are visible when set to 0 and hidden when set to 1.
>  Drive A is represented by the rightmost position of the bitmask when
>  the radix is viewed in binary mode. *Example: A bitmask of
>  10000000000000000000000111(0x7h) The bitmask above hides local drives
>  A, B, and C (rightmost bits from right to left) and drive Z (leftmost
>  bit).* 
> 
> 
> A bit mask of 11111111111111111111111111 (0x3FFFFFFh) would hide all
>  drive letters. 
> 
> 
> Administrators may also use the NODRIVES entry to disable access to
>  floppy drives on a per-user basis, replacing functionality previously
>  found in the Floplock.exe utility from the Windows NT 3.x resource
>  kits. 
> 
> 
> Drives hidden using the NODRIVES setting are not available through
>  Windows NT Explorer, under the My Computer icon, or in the File
>  Open\Save dialog boxes of Windows applications. File Manager and the
>  Windows NT command prompt are not affected by this registry setting. 
> 
> 
> NOTE: If you hide the System drive it is not available under the My
>  Computer icon or in the File Open\Save dialog boxes, however it is
>  visible in Windows NT Explorer.
> 
> 
>