Please help me get hip with new xbox 360?

So I just bought a used Xbox 360 S 250GB HD from a private seller. He has a gold account with 560 points that is still on there, along with another (a friends I guess), that expire on 6/6/12. I made a profile but some of the options are not available in the settings menu, like accounts and privacy. I was needing to know how to make it mine, so to speak, and get rid of those old accounts. I asked him to call and cancel his account, but that has yet to happen, and I also restored the machine to factory defaults.

Second, what is the "most" private was to make a live gold account? I am big on privacy and do like to give away my personal information. No Facebook, etc., EVER! Would it be best for me to buy one of those cards from a retail store? I just want to watch Netflix without telling Microsoft my blood-type, whilst their Kinect camera is watching my living room. And I though Windoze was bad with their "user data files" that save as much personal information to your computer HD as possible.

Thanks.