Maybe you have a trial version of Office 2007, and the trial
period has ended. Or maybe you have not activated your Office
software.
What happens if you start Word 2007 and click on Office Button
(that's the big round thing at the upper left corner of the Word
window) | Word Options | Resources | Activate? If you are already
activated, a dialog box saying so will appear. If you are not
activated, the Activation Wizard will start. If you have an
expired trial version, a dialog box will prompt you to enter a
valid product key or convert (purchase a key) online.