you ain't doing wrong mate, i have tried for months and months to get it hooked up, am using media centre and wireless to sort it out, but NO JOY at all!!!! Totally hacked off with it, phone microsoft's support line and they will go through all their dribble then when it still doesn't work they blame it on the router, then i phone them they go through all their dribble and still nothing and they blame Microsoft!!!! Got totally thredders with it and gave up!! Maybe try their helpline again mate for microsoft at
http://www.xbox.com/en-GB/support/contact/
Hope they can help at least it is a free call