At the start screen (the screen with the logo, picture and 'press start') press and hold IN ORDER: L2+L3+R1+ DOWN + SQUARE + CIRCLE. This will unlock all levels, skiers, outfits and skis.
Found this on ps2.ign.com Good Sites for lots of codes. Enjoy b/c I dont have PS2 and really want to play Mad TriX
##GO HUCK YOURSELF##
-Hey Harry you want to go to Aspen?
-I don't know the French are assholes
(Dumb and Dumber)