Contact them with the phone number (?) which printed on the CD box (or somewhere) and then make them re-activate your product key for you. And you have to wipe out your old computer's hard disk
Don't know if it's true, just that's what I know ;p
I have one genuine windows xp os CD. It was installed in one desktop which is now out of order. I want to instal this genuine xp version in another desktop. Please guide me so that I can do it myself.