You do not have to register XP, or give any personal details if you do not wish to. "Activation" is a a different and painless thing to do. Just click on "activate now" while you are on-line, you will see a message "Activation successful".
If for some reason it does not do as above, then phone the number given, explain your fitting of new board, you will be given a release code there ans then. Regards. j.