I just thought that I would post this for anyone who pre-ordered & pre-downloaded Call of Duty Ghost through Steam. When you are ready to play the first time, install the Multi-Player first. If not you will be forced to download the MP all over again. Follow the instructions on this link for more clarification. http://steamcommunity.com/app/209160/discussions/0/666824801165569776/
Unfortunately, I found this out the hard way and I am re-downloading my pre-download.