MW3 corrupted models

Verifying Game Cache Files (GCF)
Question

I see purple checkerboards, weapon or world models are missing, or experience crashes while playing a game - how can I verify that my game files are installed correctly?
Answer

If you have problems with missing models, video artifacts (purple and black checkerboards) or unexpected crashes, please follow the steps below to use Steam's Verify integrity of game cache feature to identify and replace corrupted Steam cache files.
Warning:

Do not run this process while performing other system-intensive processes, such as defragmenting your hard drive or scanning for viruses.

Do not run this process for multiple games at the same time.


Verify integrity of game cache

    Load Steam
    From the Library section, right-click on the game and select Properties from the menu.
    Select the Local files tab and click the Verify integrity of game cache... button.
    Steam will verify the game's files - this process may take several minutes.
    Once the process is completed, the Check Window will automatically exit.


Re-extract the Game Files for Valve games
Important:

This portion is only valid for Valve games stored in a specific user folder such as the Half-Life series, Orange Box, and Counter-Strike.

Once you have verified the integrity of your game cache files, you can make sure that your extracted game files are correct by navigating to your Steam user directory: ..\Steam\steamapps\[USER NAME]\ and either renaming or deleting your game folder.

Note: If you are playing a Singleplayer game and wish to keep your saved games, rename the game directory.

The next time you run the game, it will re-extract the files from your game cache files. If you wish to restore your saved games, copy the SAVE folder from your old game directory to your new one.