Start game, goto console (hit CTRL+PAUSE or CTRL+SCROLL LOCK) and 
enter the following cheats: 

Code       Result
-----------------
testgame - Unlock All Races, Cars And Gives You 99999 Pesetas 
allrace  - Unlock All Races 
pesetas  - Multiply Your Current Amount Of Money By 5 
winrace  - Win The Current Race (You Have To Be In A Race) 
lostrace - Lose The Current Race (You Have To Be In A Race) 
showstat - Show FPS Counter And Other Statistics