After two years of use this product suddenly giving the error message...

error code 0x8007007B

Hi,

How did you activate Office originally? By a product key or it's activated via Volume license?

We can narrow down this issue in two aspects. One is the software issue, including the factors in the system environment, the other is the licensing status.

First, please try to repair Office from Control Panel -> Programs and Features, check if this helps.

Sometimes we need to run the System File Checker to scan all protected system files and replace the incorrect versions with the correct Microsoft versions, for a Windows 7 PC:

1. Click Start > All Programs > Accessories, and then right-click Command Prompt and choose Run as administrator.
2. In the command prompt, type sfc /scannow and press Enter.
3. When the system scan is complete, try to install Office again.

If after the steps above the issue persists, I suggest you contact the customer service to check your licensing status:

http://support.microsoft.com/gp/customer-service-phone-numbers/en-us

Regards,

Melon Chen
TechNet Community Su