win xp prodeuct key changes?

Ive heard that there is a certain limit to the number of times that you can install Windows XP. If you exceed this limit then the product key of ur Win XP installation changes. Is this true?. If so, then how do you reinstall XP if the product key has changed?

Well all I do is call the toll free number and get a new activation code.

The product key does NOT change. What happens is that if you change any more than three items of hardware on the PC, then you will have to re-activate your Windows XP again either over the internet or via telephone and they will give you a new activation code.