1) To upgrade your PC from XP PRO to Vista, you will require either Business or Ultimate editions to retain your programs (a bit costly
). Vista Home Basic and Premium editions will require a rebuild and therefore your programs are lost.
I would use Vista on your laptop because XP Home can be upgraded to any edition of the operating system.
2) Why do you want to upgrade to Vista? I would wait until Windows 7 is released and get that instead. Windows 7 is more reliable than Vista. It is released on October 22.