Outlook 2007 extend.dat error

Microsoft Outlook
Microsoft Outlook 2007
Outlook 2007 error messages
How do I recover from the following Outlook 2007 error message? "An extension failed to initialize. Cannot open file: extend.dat. The file may not exist, you may not have permission to open it, or it may be open in another program. Right-click the folder that contains the file, and then click Properties to check your permissions for the folder. You don't have appropriate permission to perform this operation". I am the administrator account for this personal laptop. I cannot find the extend..dat file anywhere on my hard drive.

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Maybe you were not able to find the file because your computer is set to not show hidden files and folders. First allow hidden files and folders (from my computer, click tools and then folder options. Click the view tab. Scroll down to the option “Hidden files and folders”. Click the “show hidden files and folders” option. Click OK)

Then, try searching the file again, or go to ‘C:\Documents and Settings\<user>\Local Settings\Application Data\Microsoft\Outlook’ (this could be different depending on the OS version).

Make sure Outlook is not running. Rename the extend.dat file (to any other name). Restart outlook.

There is a Microsoft article with a similar solution here.

Discuss This Question: 5  Replies

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  • carlosdl
    Now, maybe creating a new profile might help. If that doesn't help you might want to backup your data store and reinstall Outlook.
    84,495 pointsBadges:
  • Rakei
    It has to do with some Anti-virus program, usually the error are more likely related if you are using Avast, or any malware, anti-virus program. Uninstall the program, restart you P.C and see if that fixes it. Otherwise located the extend.dat file manually and delete. restart p.c and open microsoft outlook again, This will help microsoft Outlook to reset itself. it should work. Heres the location...... Winxp: 'C:Documents and Settings<user>Local SettingsApplication DataMicrosoftOutlookextend.dat win7: cuseradminappdatalocalmicrosoftoutlookextend.dat
    3,260 pointsBadges:
  • Shuufu
    renaming the extend.dat file works. Outlook seems to have created another extend.dat file. and no more warning window comes up again. Thank you.
    10 pointsBadges:
  • Wake5
    Just in case this helps anybody below is where I found the "extend.dat" file in Win 7 64 bit... I guess Microsoft likes to move stuff around with every new operating system aimlessly and for no good reason. BTW the search in Windows did find this file, I'm sure its due to its hidden nature, Microsoft tries to hide stuff from us dummy operators so we don't hurt ourselves, or is it so we have to contact them and pay them for help when something goes wrong?? The "Wake" in the path below was my user name on the computers. C:UsersWakeAppDataLocalMicrosoftOutlook
    10 pointsBadges:
  • Gowrishgates

    Thanks you so much its work great..... :-)

    10 pointsBadges:

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