You would have registered your product at Microsoft and your new product key would come from ... Microsoft.
It's up to you to call them.
It is that simple.
I have a copy of windows xp pro that someone gave to me but they didnt give me the 25 character product key code. They moved away ages ago and i dont have any of their contact details to ask for it so now im stuck and cant install anything cause i dont have this key ive been tryin key gens etc but have had no success so far even after hours of trying. I have no experience with this sort of thing and have hardly any idea what im doing lol. Could someone please, please tell me what i need to do to find out out what the code is (and the simplest way if possible:P) Thanks heaps!:D