Quote: "Are you legally allowed to resell Windows XP Home?
If your copy is marked “Not for Resale” (usually copies that came with hardware such as laptops), You are not allowed to resell these copies of XP.
If your copy is not marked with this (typically XP Home Retail Version) you are allowed to sell your copy of Windows XP, however it is your responsibility to make sure that the buyer agrees to all the rules in the EULA."
Same is true for all Windows versions.
This is probably a better answer.
Quote: "You *can* sell it on: provided you have uninstalled it from your computer.
The OEM version is *only* for one computer, the full retail version *can* be installed on many computers provided there is only one copy at a given time.
If you activated the full retain version on one computer and subsequently install it on a different computer, the initial install (on the first computer) gets deactivated. The second computer is now recognised as running the official and legitimate copy. So if you sell it on, the buyer will get a message asking if this is a fresh install on a different computer. If he/she agrees, then they will be able to install a legitimate copy on their PC.
"
Brian.