Unless your friend bought a copy of Windows XP for you, or has sold his old copy to you (removing Windows XP from his computer and destroying all copies of the software and license), your copy of Windows XP is illegal. (You do not posess a license for it...he does.) In that case you'll be unable to download most updates, free Microsoft add-ons, etc, validate Windows, register, request tech support, and so on. Also, if this is the case you'll find no help in these forums, and we do not condone or support piracy or other illegal activities.
If he did transfer all copies of the software and license over to you, you'll have to contact Microsoft and file a change of registration so that you may proceed. That's the only way.
I got my XP cd from a friend. I want to install SP2 but it wont let me validate my cd. When i had 2K it was also given to me from a friend and i had no problem installing SPs. Is there any way to validate my copy or get around that completely so i can install SP2?