HP Compaq Presario,Presario 5116 Quick Start Manual page 21

The first time you turn on
your computer, you will be
guided through the
registration process before
accessing the Windows
desktop. It is very
important that you register
Windows with Microsoft.
Registration activates the
warranties by entering your
serial numbers in the
manufacturers' databases.
Anytime you install new
software or hardware, be
sure to register it with the
manufacturer to activate the
warranty.
To register the Windows operating system with Microsoft,
follow the on-screen instructions. After entering the appropriate
information on each screen, click the Next button to move to the
next screen.
Registering with Microsoft enables you to receive technical
support for the Windows operating system, software updates,
and notices about new Microsoft products.
If you ever need the Microsoft Product key, you can find this on
the Microsoft Certificate of Authenticity (COA) sticker on the
back of your PC.
This number is important, as it is required to access your
Windows Operating System for the first time. It is also required
anytime you restore the software to its original factory
condition.