It was because of the problems of booting and stability of the Windows O/S, that I said 'PDA'.
These have a far more stable operating system as they were designed for a particular job from the start. Windows is designed to do things between the computer (DOS) and the applications. It adds extra comlexity and cannot possibly be stable with all applications.
I expect that we shall see laptops with their 'windows' fine tuned for the application and then no other application allowed on it. This can work.