Why the (legal) notation? The only (legal) version is the one that is yours and the best one comes in the retail package. It would be foolish to try to skirt this license or try to use a (legal) version that came bundled with some other machine.
Are you ready for total data loss?
My Computer is running with Windows XP Home Edition. Now I got a original Windows XP Professional Version (legal). Is it possible to upgrade without new installation?