If u ever have to reinstall your Original Windows XP ( which i m sure u have to 
), u would normally hav 2 reactivate it again with the microsoft web site.
but there is a way around this. Just go to 'C:\Windows\System32' and look for a file called 'wpa.dbl'. Copy this file to a cd-rom. After reinstalling Windows XP, copy the wpa.dbl file back into the same folder as above and restart your computer.
edit : post ok'd by fatbeing
), u would normally hav 2 reactivate it again with the microsoft web site. but there is a way around this. Just go to 'C:\Windows\System32' and look for a file called 'wpa.dbl'. Copy this file to a cd-rom. After reinstalling Windows XP, copy the wpa.dbl file back into the same folder as above and restart your computer.
edit : post ok'd by fatbeing