Pretty much what it says in the title really. As far as I know, I have never installed a mod for Shogun 2, yet the game insists quite the contrary is true.
This wouldn't be a major problem, had it not been for the incompatibility when it comes to playing multiplayer campaigns.
Weirdly enough, the DLC-tab for Shogun 2 (clicking properties in the games library) in Steam also lists a certain 'Shogun 2 - Modder Pack Content', which I cannot recall installing. My guess would be that it came with my retail version of the game, seeing as it's listed as such.
It would be highly appreciated if anyone could shed some light on this matter. (Preferably without having to reinstall the entire game.)