Thread:Project:Support desk/Unable to install Microsoft Office add-in for Mediawiki/reply

Are you speaking of this plugin from Microsoft?

As far as I can see your error seems to come from an MSI installation process. A quick Google search shows that this error happens for other software packages as well. So maybe you want to ask in a forum about installation problems.

It seems like the problem can also be caused by some strangeness in .net. Here removing the software package to be installed (the Plugin in your case), then reinstalling .net Framework and then installing the software package worked. No idea how to remove any registry entries, which the plugin installer might already have created...