Microsoft KB Archive/249767

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Article ID: 249767

Article Last Modified on 10/7/2004


  • Microsoft Outlook 2000 Standard Edition

This article was previously published under Q249767


Outlook may perform slowly or appear to stop responding.


Poor performance can be caused by a problem with Add-ins loading when Outlook attempts to write to the Extend.dat file. If the logged on user does not have permissions to Extend.dat, or the file is damaged or in a read-only state, then Outlook appears to enter a programming loop attempting to write to this file. Quitting Outlook, deleting the Extend.dat file, and restarting Outlook often resolves the performance problem.

There are two problems. First, if for some reason Outlook is unable to create the Extend.dat file, either because the folder or the file are read-only for example, Outlook performs very slowly. The slow performance is because every event that needs to be sent to an extension causes the entire extension manager to be reinitialized.

Second, the Extend.dat file is placed in a roaming location. This is so that a roaming user can use Outlook on two different computers at the same time. Both instances of Outlook attempt to use the same Extend.dat file over the network. The second instance of Outlook opens the file read-only, and encounters the first problem.


To resolve this problem, obtain Microsoft Office 2000 Service Release 1/1a (SR-1/SR-1a).

To obtain SR-1/SR-1a, click the article number below to view the article in the Microsoft Knowledge Base:

245025 OFF2000: How to Obtain and Install Microsoft Office 2000 Service Release 1/1a (SR-1/SR-1a)


Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article. This problem was corrected in Microsoft Office 2000 SR-1/SR-1a.


This fix improves how Outlook handles communications with the Extend.dat file.

Additional query words: OL2K

Keywords: kbbug kbfix kbupgrade kbstartprogram KB249767