I know the licensing is different but... If i have the retail version, can i install it on two computers at the same time? What about OEM? Also, is there a certain number of times it can be installed and activated? One other thing...What does it mean when OEM is LOCKED to the mobo/system? Can it be reinstalled on that same system again? What about on another system? Can another os be installed on the same system? AND can i format the system i put vista on? THANKS!