Yeah but I have like 60 games on Steam, if this gets me banned my life is over, quite a risk, don't you think so? Have you tried this?
Yup, done this for both Modern Warfare 2 and the very version of Mafia 2 you have. And no, it won't get your account disabled. Contrary to the rumors Valve's fan boys, er, "moderators" like to propagate, Valve can't even tell the difference between a user with an actual IP address in the US and a user using a US based VPN. Especially as you're not even making a purchase. You are simply installing your legally purchased game.