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Error: The Add-in cannot be loaded by Outlook

Posted by Dave Mellors | Filed under Fixes to problems

After uninstalling Symantec Anti-virus I found that when I started Outlook 2007 it came up with the following error:

The Add-in “Symantec AntiVirus 10.1″ (c:\program files(x86)\Symantec Antivirus\vpnsece4.dll) cannot be loaded by Outlook. Please contact the Add-in manufacturer for an update. If no update is available please uninstall the Add-in.

The problem was that the addin didn’t appear in Tool->Trust Center->Add-ins so I couldn’t uninstall it from there.

Fortunately, deleting the file extend.dat from c:\users\<User Name>\AppData\Local\Microsoft\Outlook and restarting Outlook done the trick. That was obvious – NOT!!

NOTE: I am running Vista x64 so if your running a different version of Windows the file is likely to be located elsewhere. Possibly C:\Documents and Settings\<User Name>\Local Settings\Application Data\Microsoft\Outlook

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Tags: error, Outlook

Permalink | 12 Comments » | May 29, 2008

12 Responses to “Error: The Add-in cannot be loaded by Outlook”

1. B.I.G. DS Says:
   August 4th, 2008 at 2:17 am

   worked for me too.

   have you experienced any negative side effects after deleteing?

   so far so good for me.

   THANKS!

2. Dave Mellors Says:
   August 4th, 2008 at 5:48 am

   No side effects. The extend.dat file contains cache information and just gets rebuilt when you start Outlook.

   Thanks for letting me know the post helped you.

3. Mark Says:
   August 12th, 2008 at 3:56 pm

   Did a Google search for this add-in issue and your post about deleting the extend.dat file did the trick for my 25 users.

   Thanks!

   Mark

   Mark Cefaly
   Manager, Information Services
   Maryland Crime Victims’ Resource Center

4. D.Z. Says:
   August 19th, 2008 at 10:18 pm

   It did the work. No negtive side effect. Thanks a lot

5. IRCD Says:
   September 15th, 2008 at 3:34 pm

   Worked for me too.
   Many thanks

6. RD Says:
   September 16th, 2008 at 8:19 pm

   Thanks! your post helped me as well get from that annoying message….
   Take care
   Ronen

7. Happy ESET NOD32 user Says:
   October 8th, 2008 at 4:49 am

   Typical of Symantec uninstalls. You’d almost think they didn’t want to make it easy for you to migrate to a different AV product

8. Ron Says:
   October 11th, 2008 at 5:25 am

   Worked for me too in XP

9. ICD Says:
   October 29th, 2008 at 9:19 pm

   Worked for me, too… with F-Prot

10. Mike Says:
    November 20th, 2008 at 10:54 pm

    Thanks a lot. I was using Outlook 2007 in XP and just move to Vista, thus the interface changes make me confused. Your post is really helpful.

11. TM Says:
    January 7th, 2009 at 10:24 pm

    Hey thanks alot. I had a different addin failing after migrating outlook for my wife onto a new build. Emon.dll from nod32 was the culprit for me. Extend.dat is not an obvious solution at all.

12. Douglas Hackerott Says:
    July 20th, 2010 at 11:50 pm

    There you go – Google is your friend!

    I didn’t see this article and after using registry scanning and other utils to remove NOD32 from a migrated system so I ran Process Monitor from http://www.sysinternals.com. Sure enough, just prior to trying to read a non-existant path Outlook checks a file “C:\Users\XXX\AppData\Local\Microsoft\Outlook\extend.dat”.
    I renamed it extend.data and restarted Outlook. VIOLA! It re-creates extend.dat and the problem is solved!
    Not very obvious at all so I looked to see if I could help others solve this glitch. Beat me to the punch!

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