Try it with deleting this folder
%APPDATA%\Mount&Blade Warband\
But then I am pretty much out of ideas.
C:\Users\you_user_name\AppData\Roaming\Mount&Blade Warband
C:\Users\you_user_name\Documents\Mount&Blade Warband
Deleting this folder will delete the saves and settings. You need to try to clear all information in the registry about mount blade warband and do a clean reinstall via Steam (trying with steam again).
%APPDATA%\Mount&Blade Warband\
But then I am pretty much out of ideas.
C:\Users\you_user_name\AppData\Roaming\Mount&Blade Warband
C:\Users\you_user_name\Documents\Mount&Blade Warband
Deleting this folder will delete the saves and settings. You need to try to clear all information in the registry about mount blade warband and do a clean reinstall via Steam (trying with steam again).