Don't replace prefs.prop inside C:\Program Files (x86)\Steam\steamapps\common\the walking dead\Pack\default, delete it.
The problem is usually caused by re-installing the game, or performing a verify on your game cache via Steam, which replaces prefs.prop with a default/blank file.
Deleting the file causes it to use the prefs.prop stored with your saves, rather than the Walking Dead game directory.
If that fails to work, copy the prefs.prop file from your saves directory into your game directory. (but you shouldn't have to do that)
If you no longer have your original prefs.prop from your saves directory, then you might be in trouble.