Ok, I bought a computer and it had Windows & Ultimate pre installed, I don't have the original disks. It has been freezing up on me multiple times per sitting. I tried multiple avenues of repair, until reading that this very issue is common to W7 Ultimate. I want to change to Windows 7 Home Premium or Professional because I haven't heard of this happening to these versions. Do I have to register the version I have? Can I purchase the the other program as the upgrade? or do I have to purchase the entire package? or do I purchase a license? I am very confused right now.