...Did you click to Change Product Key
Make sure that in steps 4 and 5, you click Yes, I want to telephone a customer service representative to activate Windows but don't type anything or continue in this window
. Instead click Change Product Key
at the bottom, and enter the Product Key there.
Your product key should be 25 alpha-numeric characters, grouped in 5 groups of 5.
Activate Windows by Phone
uses an Installation ID
which consists of 54 numers in 9 groups of 6. This Installation ID is generated using the Product ID that was entered during the installation of Windows XP when it asked for a Product Key.