I currently have Windows 8 RTM on all of the computers in my house. I am very eager to buy Windows 8 in October and convert from my KMS activation to a retail, permanent activation. From what I know, Windows 8 Pro (Upgrade) will sell for 39.99. I do not quite understand what this means. I know Windows needs to be installed on the computer prior, but what I'm really worried about is will I still be able to boot from the ISO and perform a complete format? Would I actually need Windows 7 (or previous windows) instead of Windows 8 everytime I wanted to do a clean install? Simply put, when I get the product key from Windows 8 Pro Upgrade, will I be able to use this on just the standard MSDN iso without any other BS?