NASCAR Thunder 2004 Codes -

Dale Earnhardt:
To unlock Dale Earnhardt, win the Daytona 500 as Kevin Harvick (29 car). After winning the Daytona 500, a Thunder Plate will appear with Dale Earnhardt on it.

Alternate paint:
Win a race under the medium, hard or extreme difficulty setting to unlock a paint scheme for that driver.

Exhibition and alternate event races:
Win a race under the medium, hard or extreme difficulty setting to unlock an exhibition or alternate race for that track.

Night tracks:
Go to season mode and then to "Custom Schedule". You can unlock night races for the day tracks.

Alternate night tracks:
Win the race that has a locked version of an alternate night track under the veteran difficulty, 3% race length, and damage on visual only. Repeat this method on all tracks that have a locked version of it.

Road courses:
To unlock a road course for Texas, Talladega, Pocono, Phoenix, Homestead or Daytona, race the original track on the medium or veteran difficulty. 3% is the easiest race length and the fastest.