How to uninstall MSDN help files for MFC?

You can either try to uninstall parts of the whole MSDN library (using the usual uninstall procedure) or leave it there and just filter its content out in the help browser.
IIRC it's not possible to unstill the whole MFC docs separatly, but I'm not quite sure about that. Best way to find out is uninstalling all of it and applying custom settings during re-install.

HTH,
Pat.