unless you install a lot of beta software or use a lot of free/trial/p-to-p software, you shouldn't need to reinstall vista for a good 18+ months.
if you must start over frequently, consider doing an image backup after everything is installed. vista ultimate includes complete pc backup which can perform create an image backup. if you have vista premium, you'll need backup software like acronis true image.
i do a fresh copy of windows vista on my computer every 4-6 months. and i have to install al my programs and games over and over again, that takes me alot of time (6+hours).
i want a program that can implement on the windows installation my programs and games.or if exist a software that when i want to install a fresh copy of windows, only i have to do is one click. and put my computer as i was installed with my games and program the first time.
i have a 750hdd