Here is why this happens and exactly how to fix it. In Modern Warfare 3 , game data is packed into ".ff" files (FastFile). The sp_intro_ff file specifically contains the data for the very first mission introduction sequence. When the game says it "could not find" it, the game client is looking in the wrong folder—or the file is missing entirely.
If you are seeing this, your game is crashing before the first cutscene even loads. Don't uninstall yet. This is a common file structure error, and in most cases, it is fixable in less than five minutes.
There is nothing more frustrating than firing up a classic Call of Duty game, ready to relive the Price vs. Makarov showdown, only to be met with a black screen and a cryptic error message: "Could not find zone 'sp_intro_ff.'"