Can we get your T.V. model number to check out its statistic's for possible solutions. Give us the model number off the back, should be next to the manufacture date. Also do you have access to all of it's features? Can you access all sub menu's on your T.V.?
My first suggestion would be your television may not be in the proper aspect ratio for your Xbox settings.
There is the possibility there is no fix, but maybe we can help solve something.
Also if you can additionally list all of your settings off of your xbox display settings, and all your tv's picture settings.