when you turn it on, when the nintendo sign turns up quickly press and hold x,y,a,b,l,r
and it should come up with a prompt saying do you wish to delete all your saved data, say
yes, are you sure, yes and so on, but it takes a while to delete

thanks i needed to know how to do that ta

while the game is loading hold l,r,a,b,x and y then it'll ask you if you want to delete
data, click 'yes' and it will reset EVERYTHIN!

hope this helps :)