Where to buy a cheap and legit Call of Duty cd key?

You can use the administrator key codes, which are free, and unlock the game, legally, it was made for the Devs. Look and see if they have any.

ahah:D I'm not a newbie! Grrr .. Everything is OK guys :D Bought MF3 and Battlefield 3 for 25 bucks from "HitGamesStore dot com" and it works fine :D

Try going to the developers website and checking if you're able to buy a key from them. Didn't your game come with a key?