Enter these cheats at the Main Menu:
Effect: Code
Skip Next Beat in Heat Scenario: Up, Down, Left, Right, White, Down, Down
High Suspension: Up, Down, Left, Right, White, Up, Down
Mini Cars: Up, Down, Left, Right, White, Down, Up
View Credits: Up, Down, Left, Right, White, Left, Left
Wire Frame Cars: Up, Down, Left, Right, White, Right, Left
Shoot Paintballs: Up, Down, Left, Right, White, Up, Up. (Press Up on the D-pad to shoot the paintballs)
Hardcore Realism Mode: Up, Down, Left, Right, White, Up, Down. When done properly the options on the screen will scroll to the left then back to the way they were before.
Unlock Richard Petty: To race as Richard Petty, successfully complete all heat challenges with a bronze or higher rating.