Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
This happen if the office setup files in machine is corrupt. Remove all the instances of office keys from the registry to fix this issue. Follow the steps mentioned in the article below:
Note: Back up the registry before you modify or delete any key: http://windows.microsoft.com/en-us/windows7/Back-up-the-registry
To remove Office check: http://support.microsoft.com/kb/928218
Ruchi Bisht