Extract SweetFX files in the root directory. Game has to be played on "Medium" settings, changing it to "High" or "Very High" disables SweetFX, I assume the game applies AntiAliasning which interferes with SweetFX but is disabled in-game when "Medium" or lower is selected, unless someone manages to find away to disable in-game AA via another means, you must play at "Medium" if you want SweetFX working.