Are you sure? As far as I'm aware, I'm able to install a game I own on multiple machines for all of these platforms. I figured that the game is tied to my account, not some hardware ID. Why would they need to make sure I'm not charged twice based on installing the game to a machine rather than just seeing if my account owns it? I have never been charged more than once for a game I own that I have installed on both my desktop and my laptop, even after replacing those machines.