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Q253821: System Error 85 with "NET USE" Command

Article: Q253821
Product(s): Microsoft Windows NT
Version(s): winnt:4.0,4.0 SP4,4.0 SP5
Operating System(s): 
Keyword(s): kbenv kberrmsg
Last Modified: 06-AUG-2002

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The information in this article applies to:

- Microsoft Windows NT Server versions 4.0, 4.0 SP4, 4.0 SP5, Terminal Server Edition 
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IMPORTANT: This article contains information about modifying the registry. Before you 
modify the registry, make sure to back it up and make sure that you understand how to restore 
the registry if a problem occurs. For information about how to back up, restore, and edit the 
registry, click the following article number to view the article in the Microsoft Knowledge Base:

  Q256986 Description of the Microsoft Windows Registry

SYMPTOMS
========

When a non-administrative user attempts to reconnect to a shared network drive
that the user has already used, system error 85 ("Local device name already in
use") may be generated.

For example, running the following sequence of commands in a logon script or from
a command prompt illustrates the issue:

  net use r: /d
  net use r: \\<servername>\<share>
  net use r: /d
  net use r: \\<servername>\<share>

The behavior does not occur for users with administrative privileges.

CAUSE
=====

This behavior is caused by a setting of 1 in the following registry value:

  HKLM\System\CurrentControlSet\Control\SessionManager\ProtectionMode

If the setting is 1, the problem occurs. If you change the setting to 0 and
reboot the server, the problem disappears.

Note that the following articles in the Microsoft Knowledge Base suggest changing
this value to 1 to restrict changes to Base System objects and for solving
problems with symbolic links:

  Q218473 Restricting Changes to Base System Objects

  Q244995 Base System Object Restrictions Are Not Enabled by Default

  Q222159 Symbolic Link Case Sensitivity Exploit Bypasses System Security

WORKAROUND
==========

WARNING: If you use Registry Editor incorrectly, you may cause serious problems
that may require you to reinstall your operating system. Microsoft cannot
guarantee that you can solve problems that result from using Registry Editor
incorrectly. Use Registry Editor at your own risk.

Change the entry for

  HKLM\System\CurrentControlSet\Control\SessionManager\ProtectionMode

from 1 to 0.

Additional query words:

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Keywords          : kbenv kberrmsg 
Technology        : kbWinNTsearch kbWinNT400search kbWinNTSsearch kbWinNTS400search kbNTTermServ400 kbNTTermServ400sp4 kbNTTermServ400sp5 kbNTTermServSearch
Version           : winnt:4.0,4.0 SP4,4.0 SP5
Issue type        : kbprb

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