Mount & Blade: Warband
From PCGamingWiki, the wiki about fixing PC games
Mods
To install Mount and Blade mods, navigate to your Steamapps 'mountblade warband' folder, and extract the mod in the 'Modules' folder. Then select the mod from the drop down menu in the launcher when you first start the game.
Mount and Musket
You can get the Mount and Musket mod from This link, which adds muskets and cannons to the game.