Office installed on top of Office

When Office is installed over a previous copy of the same version, and the install is then aborted, every time an Office application is started it tries to complete the aborted installation.

Q1. There’s a name for this situation, what is it?

Q2. Am I right to think that a complete uninstall followed by a fresh install is needed to fix the situation?

I knew the answers to both these questions when a friend asked my advice on Boxing Day 2005. Now he has asked me to repeat the advice so he can ask his support team to do the necessary and my mind is a complete blank.

Can somebody help?