Step1 - Go to this link --> http://www.nintendo.com/consumer/systems...forgot#nextStep
Step2 - Follow the instructions to get an inquiry key.
Step3 - Enter the inquiry key into the field at the bottom of the webpage and click continue.
Step4 - You can either choose to call or chat with Nintendo Support. I chose chat myself so I would recommend you do the same.
Step5 - The Chat Support agent gave me a master code which I entered into my DS and it reset the parental controls.