Click on the Start Orb, lower left corner of screen
Click on Control Panel
Under the Programs Heading:
Click on: Uninstall Programs
Scroll down to the Microsoft Office version you have installed.
Select the version, DO NOT DOUBLE CLICK,
simply highlight the version.
If you now look at the Options bar near the top of the screen
it should display a Change option.
Click on the Change option and select Repair.
Depending on what is wrong you may need your original install media.