The picture is too big for my screen

Press zoom on the remote control to get the normal size

Normallly, if the picture size button on the remote for the television does not achieve the desired affect, then, a cable box or a satelite box is where the change needs to be made.
For example:
A Motorola Cable box needs to be set up to go to a wide screen or zoom when an analog signal is detected.
Some Dish Network boxes have Size buttons on their remotes and also in their main menu.
It's difficult to determine the repair without knowing the types of the peripherals.
Hope this helps.