installing xp over an existing copy of xp

[davy90]

 I have a computer with a "non validating" copy of windows xp                                    ( bought ,unsuspectingly, from a friend) . I have now obtained a legit copy of windows XP. How do I proceed with the installation?

Thanks

[Carbon Dudeoxide]

Not so sure, but you should be able to validate Windows with the new license you just bought.

[JJ 3000]

Or you could just do a clean install. If you just bought the computer, then that would probably be the best route to go.
Look at this:
http://www.michaelstevenstech.com/cleanxpinstall.html
good luck.