NASCAR Thunder 2003 Cheats

Unlock Extra Drivers
Enter Extra Drivers as your name when you create a driver.

Unlock Dale Earnhardt
Enter Dale Earnhardt as your name when you create a driver.

Unlock the Tiburon Speedway
If you have a savegame from any other EA Sports 2003 title you will unlock the Tiburon Speedway track.

Unlock the Tiburon Speedway
Another way to unlock Tiburon track is to play the lightning challenges. One the challenge when you play as Harvick at Atlanta (or at least thats the way it was for me) you will unlock Tiburon track. This track has top speeds at nearly 240 MPH, it is 3 miles long, all banking, and looks like Talladega, except that you race backwards.