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Article ID: 893231 - Last Review: October 9, 2011 - Revision: 4.0

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If you try to open a mapped Distributed File System (DFS) folder, you receive an error message that is similar to the following error message:
drive letter:\ is not accessible.

Configuration information could not be read from the domain controller, either because the entire machine is unavailable, or access has been denied.
This symptom occurs if the following conditions are true:
  • The DFS folder is available for offline use.
  • You are logged on in offline mode.
  • You used cached credentials to log on.


A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site: (
Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.


To apply this hotfix, you must have Microsoft Windows XP Service Pack 1 installed.

Restart requirement

You must restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace any other hotfixes.

File information

The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.
Windows XP with Service Pack 2 (SP2)
   Date         Time   Version      File name
   12-Apr-2005  5:41   5.1.2600.2653  Mup.sys
Windows XP with Service Pack 1 (SP1)
   Date         Time   Version        Size   File name 
   10-Nov-2005  00:58  5.1.2600.1772  105,216  Mup.sys


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.


For more information about a related topic, click the following article number to view the article in the Microsoft Knowledge Base:
840749  ( ) You cannot open a mapped offline-files drive during CSC synchronization in Windows XP
For more information about the standard terminology that is used to describe Microsoft software updates, click the following article number to view the article in the Microsoft Knowledge Base:
824684  ( ) Description of the standard terminology that is used to describe Microsoft software updates
kbautohotfix kbqfe kbhotfixserver kbwinxpsp2fix kbwinxppresp2fix kbfix kbbug KB893231
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