To fix this, you will need to do a few things...
1. Download a 1.1 DVD/disk version executable to replace the one you currently have in your GameData folder
2. You will probably need to replace your shell.lvl with a DVD/disk one as well
3. Rename your parent folder for your GameData folder from 'Star Wars BattlefrontII' to something else e.g. 'SWBF2'
4. Make sure you change what executable GameRanger is using (you want it to select the one you replaced) by going into options and finding it manually.
Download:
http://www.mediafire.com/file/mu4b17c248glm4x/BattlefrontII.exe Steam Directory for GameData folder: Windows (C:) > Program Files (x86) > Steam > SteamApps > Common > Star Wars Battlefront II > GameData
Unfortunately, I can't help you with finding the proper directory if you're using the GOG version because I don't own it.