Ok, so I installed Vista Home Premium on my Laptop using my friends disc and his serial, to try it out and see if I wanted to buy it. Well the 45 days or so ran out and now it needs me to put in the serial again. Well, I cant get the serial again, and I am confused on which Vista I want to buy now. If I get the full version of Windows Vista Ultimate am I wasting my money because I could just use the Vista Ultimate update disc? Or, will I even be able to upgrade without the original product number?