Use Any Car on Any Track
At the DOS prompt, get to the directory where you installed Big Red Racing. Once you're there, start the game with the command:
Replace (car1) and (car2) with the cars you wish to use. Start the game and go to the Car Select screen. The vehicles you selected should be available.
An example would be: "racing -car ATV -car Feheli". You can figure out all of the car names by opening up the directory where BRR is and using the names of the .VHC (vehicle) files.
Note to demo users: The hovcar does not work and you can only race against the Feheli.
