Need for Speed: Underground Cheats (GameCube)

Unlock all drag tracks, unlock all drift tracks, 
unlock all circuit tracks, unlock all sprint tracks, unlimited nitro 

AT THE MAIN STAR MENU, ENTER THE FOLLOWING:
Unlock All Drag Tracks

Right, Z, Left, R, Z, L, Y, X
Unlock All Drift Tracks

Left, Left, Left, Left, Right, X, R, Y
Unlock All Circuit Tracks

Down, R, R, R, X, X, X, Z
Unlock All Sprint Tracks

Up, X, X, X, R, Down, Down, Down

All you do is use your car in single player drift mode.  Use the first 
track and you can gain lots of points.  I have gotten over 60000 points 
on this track!

You will notice when you start need for speed there will be a goldish 
colored Nissan skyline saying eastside boys on it but you cannot seem to 
select it. To unlock this car you need huge amounts of style points 
achieved by doing races and other events. It is advised to complete all 
the races in underground including the 112th race. Once you have done 
that you should have loads of sty;e points. If you still dont get it go 
on quick race and select a finely tuned car and win as much points as 
you can on drift mode. You will achieve lots of style points that way. 
Also you may unlock many other cars including Samantha's.