About Office and Windows XP Product Activation and Licensing
Recent versions of Microsoft Office and Windows require you to "activate" the product after installing it. If you don't activate it within a certain number of uses, the product goes into a reduced functionality mode in which some many editing and saving features are disabled.
Microsoft's explanation of Office Activation
For an explanation of the various types of Office XP and Office 2003 licenses and links to other articles read this
There's also this Microsoft Product Activation FAQ
Microsoft's explanation of reduced functionality mode. Office XP products go into reduced functionality mode if not registered within the allowed number of uses.
How to activate a license for Office XP or the standalone versions of the Office XP programs (PowerPoint 2002, etc.)
To activate Windows XP
You can open the Windows Product Activation wizard by clicking Start, then Run, and type in
We don't make this stuff up. Somebody does, but it's not us.
The Wizard will explain how to activate Windows over the internet, via modem or by voice telephone call.