That doesn't show if a key is unused though.

Thanks for the tip! But as Tristar mentioned, I can't tell if the key is used by someone else, just that it's a key for the game that I already have... But like I said, I'm pretty sure it's a good key. I recently bought the game (not realizing I had this key from a while ago), so I know for a fact I didn't activate it. And I'm also almost positive I haven't given the key to anyone else. I don't have any memory of ever giving away any of my humble bundle keys...