Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Have you tried repairing the Office suite?
The Office installation could be damaged or corrupted. Repair the Office suite and check if it helps.
Refer the following link to know how to repair the Office suite:
http://support.microsoft.com/kb/924611
If the issue persists, remove and re-install the Office and verify the result.
To remove Office 2007, use the FIX IT from the Method 2 in the below link:
http://support.microsoft.com/kb/928218#Method2
Note: Ensure you have the disc and the product key for Office to re-install.