i have had a copy of xp pro for a few years. everytime i replace my motherboard, psu, and even psu, motherboard, cpu, and memory a message would pop up at the beginning of a boot saying my hardware has changed significantly please re-activate xp. i like my copy of xp pro and i wanted to know if it was ok for me to believe that i shouldnt have to buy another copy. the hardware that i had usually replaced i put in a new case and gave the pc to my son and he bought a new copy of xp to install on it. its gotten to where everytime i install xp pro i have to call microsoft to activate by phone. one microsoft operator on the phone said to me that the xp os has to stay with the pc.