will there be a perfomance change If I upgrade my windows 7 to windows 8.1 from the option "keep window settings,personal files, and apps" *in other word, without formatting the main windows partition* ?
as shows in the video : http://www.youtube.com/watch?v=RWLzNExKSpw
as shows in the video : http://www.youtube.com/watch?v=RWLzNExKSpw