My grandmother has windows xp on her system. Obviously we all know the crazy and cruel things that now happen when you use windows xp. So I want to install windows 7 for her. She would like to buy it from Amazon. My question is a two part question: which basic version would she purchase, the upgrade or just the basic windows 7? Second, would I have to reformat her computer to install it or just pop the disc in and let it do its thing?