I am building my first computer. When I buy an O/S, what should I be looking for? I've heard that if I buy an O/S that has OEM in it's title that I won't be able to upgrade my MO/BO in the future without buying another O/S. Also, I heard that Microsoft won't support Windows 7 in a few years. I want an O/S that I can depend on it being viable for the future. Thanks!