When you receive and error that Outlook can't find and add-in, the usual cause is that you uninstalled it but Outlook didn't delete the file it uses to keep track of installed add-ins. This file is extend.dat and is found in the (hidden) local app data file under your user account. It's in the same folder as your Outlook data files.
You can quickly jump to it by typing or pasting the following command in the Start Search field in Windows 7 or Vista.
Delete it and restart Outlook. Outlook will rebuild the extend.dat field and the errors should go away.
In most cases, you'll need to restart Outlook for any changes to take effect.
Tip: when you use these commands to open hidden files and folders, you can see the contents of the folder without changing your settings for Hidden files and folders.
Windows XP Location
If you are using Windows XP, extend.dat (and the data files) are at
%USERPROFILE%\Local Settings\Application Data\Microsoft\Outlook
Type or paste it into the Start menu, run command (you can also use Windows key + R to open the run command) and press Enter.
Open the Add-ins Dialog
To view the installed add-ins, go to Outlook 2007's Tools menu and select Trust Center, then Add-ins. In Outlook 2010, you'll go to File, Options, Add-ins. The list of installed (and the active or disabled state) is on this screen. Click Go at the bottom of the screen to open the dialog which will allow you to enabled or disable the add-ins.
In older versions of Outlook, go to Tools, Options, Other, Advanced options, Add-in Manager and COM Add-ins.
Delete Extend.dat Video Tutorial
For more information on shortcuts to the file locations, see Where Are My Files? (Outlook-tips.net)
For more information on the files Outlook uses and which need backed up, see Outlook 2007 Backup and File Locations
How to query version of pst file because outlook2002 questions opening it? Warning posts contact admin because pst incompatible or wrong. Some pst that successfully open don't jive with its size, missing mssgs, or empty with deleted icon empty too.
2002 won't report the pst type (ansi or unicode) - it can only tell you that it's not compatible. Outlook 2003 and above will identify the pst type. If the pst is over 2GB, 2002 won't be able to open it.
Are you sure the pst is the wrong type instead of corrupt?
i use office xp but outlook will not open archive pst files from my employment outlook i copied and brought home to my pc.
i do not understand whether archived pst files are not ok or my home xp os pro sp3 is not compaible with xp office loaded
some pst files do open but appear incongruent with the pst filesize 1.9gb where limit is 2gb in 2002 office version.
for each pst archived there is an accompanying file with the pst file called extend.dat, dunno whether i must delete it 1st before opening it in outlook (not import pst for it does not work! causes crash corrupt)
extend.dat isn't important - it is a support file that shows what addins are installed.
While we say the the pst size limit is 2GB, it's actually 1.9 GB, so it sounds like the pst are at the max if they are ansi pst files. They could be slightly oversized and corrupt as a result. Try installing one of the trials for pst repair - they will let you look in the pst. Any of the utilities (with free trials) on this page should work - https://www.slipstick.com/problems/pst-repair/repair-a-2gb-personal-folders-or-offline-folders-file/
What version of Outlook did you use at work? either the pst are corrupt or created in the newer versions.
I use Outlook 2003 on my PC. I deleted the file & restarted outlook, but am getting the alert, Intel Wireless Bluetooth: & the programme has, 'stopped working'. Do I follow the same procedure?
Go to File, Options, Other, Advanced, Addins see if there is a Bluetooth addin listed - if so, uncheck it. If the addin didn't exist, deleting extend.dat would remove it from outlook, but since it sounds like you deleted extend.dat already, the addin may be installed.
didn't find any info on 2013
Extend.dat is in the local app data folders for all outlook versions, the operating system controls the actual path to that folder. Because Outlook 2013 is only supported on Windows 7/8, extend.dat is in the Win7 location - %localappdata%\microsoft\outlook