Apparently, you have a trial version of Microsoft Office installed and the trial period has ended. In order to continue to use Microsoft Office, you'll have to purchase a Microsoft Office license (product key).
How to convert a trial version of a 2007 Office suite or program to a full retail perpetual license version:
http://support.microsoft.com/kb/927756/en-us
Note: The product key affixed to your computer is for Windows Vista and not for Microsoft Office 2007.