There's 2? I only found the one in the Steam folder.
The one in the install dir does nothing for Vista/7/8 afaik
The two you need to change are here
\User\AppData\Local\4A Games\Metro 2033\user.cfg
Only problem I've found, even setting 'read only' the game still reverts them back once you exit the game and you have to edit them again the next time