You practically buy the key code from Microsoft, and the CD with the Windows' files just come as a bonus. It doesn't store your code anywhere, there is an advanced rule how these codes are generated, and each and every one of these can be used once at a time to register. They know what codes have been generated officially, so even if you find out the code rule, you can't generate your own to cheat.
-In.Dev.X: A unique heavy story based shoot'em ~35%
-CoreFleet: An underground commander unit based RTS ~15%
-TailsVSEggman: An Sonic themed RTS under development for idea presentation to Sega ~15%