if you pay for a game you get a product key and with that you register your game and you sign in and play multiplayer if. if i install the game again on a different pc can i still sign in with my account or will it ask me for a product key or worse ask me for one during installation. i want to know this because im buying a new computer and was wondering if i have to buy all my games like modern warfare 2 and bad company 2 and so on