A: Not recommended. You can remove orphaned MSI references using msizap.exe (part of Windows SDK), but one wrong move can break all Office apps.
Sometimes, the Officemui.msi error indicates a deeper problem: your Office installation is mixed (e.g., Click-to-Run alongside MSI-based). If you cannot resolve the error after multiple attempts: Officemui.msi Download
If you are stuck at a dialog box right now, follow this exact sequence: A: Not recommended