How to turn of parental controls on a xbox 360 slim?

I got an xbox 360 slim on ebay and the parental controls will not let me watch game ads or some xbox live content. I go to the parental controls and it asks for a 4 digit code, so I enter in a wrong one so it asks me if I wasn't to reset, I say yes and it takes me to a security question that I don't know the answer to because it is from the previous owner. Is there any way to override it at all?