Simple. When you use it you need to activate online. The activation proves it is legit. There is not much else I can offer except to give you my information when you buy them.
I believe you when you say they are legit, but above is not a true statement.
I have reinstalled Windows, on literally thousands of different computers. They were all previously activated. After the reinstall using the original media and code, the
online (i.e. no need to call) activation worked with no problem. They usually give you a few activations before making you call.
