How-To: Fix Trend Micro Add-In Missing in Microsoft Outlook

This post will be the first of many that I plan to write that detail some bugs, technical issues, and problems I’ve had to fix in some way.

I had a friend come to me with an issue: Every time they started up Outlook, they received an error saying that the Trend Micro add-in was missing. Reinstalling Trend Micro did not correct this issue. I thought this was going to be an easy fix. I started by trying to disable the plugin via the Tools/Options area of Outlook. Unfortunately, there was no listing for anything from Trend Micro. Yet, Outlook seemed to think there was something.

One solution I found online was to delete the extend.dat file that Outlook uses to know which extensions are installed. On Windows XP, that is found at:

C:\Documents and Settings\%username%\Local Settings\Application Data\Microsoft\Outlook\

On Windows Vista and Windows 7:


Once this file was deleted, I reopened Outlook. Outlook rebuilt the file, and we never saw an issue with a ghost Trend Micro plugin again.

Did you find this solution helpful? Or did you find another solution to this problem? Leave a comment!

2 Replies to “How-To: Fix Trend Micro Add-In Missing in Microsoft Outlook”

  1. thanks josh worked with me aswell 🙂

  2. You’re welcome! I’m happy to know that something I wrote over two years ago is still useful.

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