Usually it's either because you haven't activated your Office software, or
because you have an expired trial version of Office 2003. What happens if
you start Word and click on Help | Activate Product? If you're already
activated, a dialog box saying so will appear. If you're 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 purchase a key online.