* Open Outlook with "run-as-administrator"
* Go til File
* Click Options
* Go to Add-ins
* Click GO in "manage COM Add-ins"
* Locate "proNestor Booking for Outlook" that points to a location of an "PronestorOutlook2004AddIn.dll"
* Remove that one
* Ensure that the remaining "proNestor Booking for Outlook" is active by enabling the checkbox
* Restart Outlook