'upgrade / repair' install option

I'm working on upgrading some builds and similar to the issue/flaw wherein selecting a language can only be done once without some convoluted work to revert temporary config/registry entries - if you don't execute the installer the first time as administrator, you seem to lose the ability to access the 'Select installation mode' screen any attempt thereafter as the same user.

I'm trying to determine what registry entry or temporary files (assuming at the user level) need to be changed or outright removed in order to see the 'select installation mode' screen once again.