I ran an installer that provides a plug-in, PluginA, to the program "ArcMap.exe". Later I tried to remove this program but this did not work. The problem seems to be a bug in the plug-in installer.
I browsed the web and found the tool "Windows Installer CleanUp Utility 7.2" which I installed. I ran this utility and managed to remove the plug-in. However I noticed that when I started Outlook it had to configure itself every time :-(. Therefore I unistalled the utility.
Next I installed another plug-in to the program "ArcMap.exe", PluginB. This installer I know to be bug free. However when I start ArcMap.exe it displays "Please wait while Windows configures PluginB" and this process never ends. I have tried uninstalling PluginB and that works, but I need to have PluginB installed.
Also I still have the problem with the windows installer running each time I open Outlook.
To me it seems that "Windows Installer CleanUp Utility 7.2" has messed up my Windows installation. How do I fix this? Unfortunately I have not been wise enough to have any useful System restore points.