listen up idiots... if it says "missing config file ' default_mp.cfg' either you dont have the mulitplayer version installed or you need to reinstall it.. simple as that. when you open steam their is 3 downloads to call of duty bo2 (Call of Duty: Black Ops 2) (Call of Duty: Black Ops 2 - Multiplayer) and (Call of Duty: Black Ops 2 - Zombies) Just download them all.