Unlock the Black Box Classic car:
     Win the Short Track Challenge.

Unlock the Black Box Exotic car:
     Win the Half Season.

Unlock the EA Sports car:
     Win the Road Course Challenge.

Unlock the EA Dot Com Car:
     Win the Superspeedway Shootout in either veteran or legend.

Treasure Island Track:
     Win the full season on veteran level.

How to make it a demolition derby:
     Select single race and any track (Daytona is the best choice) and
any driver. Set damage on limited and the race length to 100%. You can
either  race in happy hour or the actual race. Go either the wrong way
or  the  right  way. When your car get's flipped over then it will say
"hit gas to reset" (X). Now start the demolition !

John Andretti's 2nd car:
     Go to the options menu and choose the credits option. Then select
development.  After the FMV the credits for the development will start
to  roll.  Now  enter  the  following code: Hold R1 then press Square,
Triangle,  Square,  Triangle  then you should hear "Oh Black Box Baby"
that the code has been confirmed.

Proving Grounds:
     Go to the options menu and choose the credits option. Then select
development.  After the FMV the credits for the development will roll.
Now  enter  the  following  code: Hold R1 then press Left, Circle, Up,
Down,  Right,  Right,  Right  then you should hear "Oh Black Box Baby"
that the code has been confirmed.