I'm building a new computer, and I need to get an OS and windows was the only option for gaming. I didn't get an optical drive cause I would never use it and I heard that I could just use a usb flash drive for my OS. My brother is a student, so I want to get that 'upgrade to windows 8 pro' deal ($70) and I need it in idiot's terms how I do that. (I have a computer with windows 7 right now if that is needed)