At the Main Menu, type any of the following "Codes":

Code                    Effect 
imacheater              Enables Win Button (Ctrl + W) 
ineedmorecars           Unlocks All Cars 
ineedmoremaps           Unlocks All Maps 
championsaves           Enables All Classes 
gokartz                 Little Wheels 
bigheadz                Big Heads for Drivers 
bigfootz                Large Wheels on Vehicles 
boxerz                  Big Hands and Feet for Drivers 
greasy                  Slippery Surface 
glued                   Very Gripped Surface 
terraformer             Opens Up the Map Generator 
manonthemoon            Moon Gravity 
teachme                 Pre Instruction Screen 
celebration             Congratulation Instead of Race 
fontkart                Secret Level 
speedracer              Fast Race 

Various Cheats - US Version

     At the Main Menu, type any of the following "Codes":

Code                    Effect 
monstertruck            Big Wheels 
rollerbearing           Little Wheels 
moonwalk                Low Gravity 
fistfighter             Big Hands for Drivers 
balloonnuts             Big Heads for Drivers 
winbycheat              Enables Win Button (Ctrl + W) 
fillmygarage            All Cars 
worldtraveller          All Maps 
kingofthehills          Map Generator