Re: Question about Windows XP PRO...
since you use XP pro you will not have experienced this activation issue as XP pro does not use it by default. It only seems to affect XP home. Basically activation turns the CD key into a unique ID for your computer and sends this back to microsoft. Then if the same key is activated elsewhere microsoft will see this and go "no, You are not allowed this" and will block use from activating, and thus using XP altogether.
XP pro does not ask you to do this, unless you actually opt to do it. Hence many installations can use the same key without being blocked after 30 days.