Here is what I do:

I download the FREE version of Revo and run it

It will give you a listing of programs that can be uninstalled

Select Office

As it Uninstalls, and this is the critical part: you will see a list of Registry Keys to select, and you want to Select All, because you do NOT want these keys to store anything, because otherwise, you will be reinstalling with these old Registry Keys

Now, after you have Uninstalled Office, reinstall

You will now have a "virgin" copy of Office installed

WARNING: MAKE SURE YOU HAVE ANY PASSWORDS, ETC, YOU MIGHT NEED TO REINSTALL, BECAUSE THERE IS NO GOING BACK