If you have any other hard drives or ssd's, it is a good idea to go back and select those drives and delete the DirectX Shader Cache on them (if the size next to it reads "0 MB", there is none on that drive). Uncheck everything except "DirectX Shader Cache", Then hit Ok.
Delete all files inside both of these folders. There are two key folders here, "DXCache" and "GLCache".
Navigate to your install directory (if you do not know this, select Call of Duty: MW in and click Settings > Show in Explorer).This is going to go over everything people have tried to fix this, ordered so it can be done all at once. They reverted the way shaders are installed.