So I am using Vista RC2 on my desktop as my only OS and the expiration date for it is nearing closer. Now, I have a copy of Vista Home Premium that I want to format and install temporarily (~1 month), without activating because I am eventually going to put it on another computer, until my copy of Vista Ultimate arrives from the school. So my question is, would it be alright to upgrade from Home Premium to Ultimate or should I just go ahead and reformat and install afresh again?