Bad comppany 2 Online Authentication

My old man just bought Battlefield:Bad company 2. He does not use the online feature at all he just likes to play single player.

the Game is installed on 2x PC and i want to play online without using the CD on my pc but it askes for CD.(cant find a no-cd crack for it either). Can some1 who perhaps has use online authentication explain how it works plz.

the games are already installed but require CD to play, can this be changed without reinstall?

when u use this feature how exacly do they know what PC u are going to install on like to they give you a password or something?

would i have to unistall on both PC?

The game is very cheap atm i think i might just go out and get it but if there is a chance this would work without issues saves me 50 bucks.  

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