Hold X + Y at the options screen. Select the "Password" option 
that will appear. Enter one of the following case-sensitive 
passwords to unlock an additional course: 

Enter CinqueValvole to unlock the Fiorano course.
Enter LiebeFrauMilch to unlock the Nurburgring course. 
Enter Stars&Stripes to unlock the Laguna-Seca course. 
Enter KualaLumpur to unlock the Sepang course.
Enter DaysofThunder to unlock the Atlanta course.