So if you're using the free version (Days 1-13), the patch file provided will break the game.
If you downloaded the lightly compressed version of Days 1-16, you only need to extract those files and boot the .exe up from within.
If you downloaded the uncompressed files, the same thing is required - you just want to make sure you're on the right version of the game. This error occurs when the versions are mismatched.