You can modify or change product key for 2007 Microsoft Office programs or suites by first uninstall or remove Microsoft Office and then reinstalling the business productivity suite. You may need to alter or change Microsoft Office 2007 (aka 2007 Microsoft Office System programs and suites) product license key or volume license key (VLK) which also known as serial number or CD key.
How to Reset or Change Microsoft Office 2007 Product License Key or Volume License Key (VLK)