Instructions
Begin the game, and select "Options" in your game's main menu.
Change one of your game options, then select the "Exit" option. Wait approximately 1.4 seconds, then power off your DS.
Turn your DS back on and try to play the game. You should receive a "Save File Corrupted" message, at which point you will begin the game with your save file deleted. If you do not receive this message, repeat the process until you do.