Hey guys, so I'm in the process of buying components to build my own PC. Well I'm for sure going to be using Windows 7 as the operating system, but my friend told me that I shouldn't pay the full price for it. He said that he has the disk to install Windows 7 Pro and that all I needed to do is buy an product key online. Can this actually work? If so it this legal? And where can I buy a product key? Any help would be appreciated! Thanks!