First, let’s get one thing out of the way. Microsoft’s been all over the map when it comes to whether System Builder licenses can be used by normal computer enthusiasts building their own machines. On Windows XP, Vista, and 8, this was allowed. On Windows 7 and now 8.1, it’s not allowed. But you wouldn’t know it unless you read the fine print. For the purposes of this article, we’re just going to assume that you can actually buy and use a System Builder (or OEM) edition of Windows and use it on your own computer.