A few points worth considering.
1. Run Files and Settings Transfer Wizard to create a full backup of all
your personal data, application data, email, internet favourites, passwords
etc. Save this to a file on your hard drive and then copy to CDs.
2. When you get the new PC run FAST and import the file from the old PC.
You can use a network connection between the two or use the CDs.
3. Format the Hard Drive to wipe all your personal information. Doing this
as part of a fresh installation of XP will save time.
4. Hand over the PC with all user manuals and COA, plus Product Keys: the
new owner can then enjoy the experience of setting up their own user
accounts, installation of application software and internet setup.
5. Once they are on the web the can activate Windows: they may need do this
via the phonbe to explain why they are reactivating.
This resolves all your problems: register new owner, save your files, delete
personal information from old PC and quicker setup of the new PC!