I have a homebuilt desktop and a HP Pavillion Notebook that came with Media Center installed. At some point I rebuilt my PC and loaded XP Pro on it and then later did a reformat on the notebook and decided to load XP on that also. When I called Microsoft for the code to load on the notebook I explained I was converting over to XP with a copy I had put on my PC and they said it was ok for one notebook and that was their policy. Maybe the phone tech was confused or charitable but he gave me a code and both machines have been running since on the same license for XP Pro. I get notified of all updates and it lets me load them on both machines. Hope this clarifies my post.
In my old age I do forget details but I think I remember this one ok.
Thanks again.
Soapy