Instructions
Turn on the Nintendo DSI and touch the wrench icon to open the "Settings" menu.
Scroll to the third page of options and hit "Parental Controls."
Touch "Yes" to confirm that you would like to change your controls. At this point, you will be prompted for your PIN.
Tap "I forgot," and then touch the empty box at the bottom of the screen. The Nintendo DSI will prompt you with your security question.
Type the answer to your security question into the box and hit "OK." At this point, you will be able to set a new PIN.