Instructions
Start "Pokemon SoulSilver" and advance to the title screen.
Press "Up" on the directional control pad, the "Select" button and the "B" button at the same time. Your top screen will display a prompt that asks, "Delete all saved data?"
Press "Up" and then press the "A" button to select "Yes." The game will warn you that deleting your save file is permanent and also deletes data registered on your PokeWalker accessory.
Press "Up" and then press the "A" button to select "Yes" again. Your save file will be deleted from your game card.