Hi and thank you for using justanswer.I`m going to help you with your tv but first i will have a few questions;
Could you please lookup your tv`s model number on the back cover ?
If so then look on your cable box`s remote control for a button called format,zoom,size etc.
As you appear to be offline , i will switch to standard Q&A mode.
Thats o.k for now.
Do you have a cable box ?
And can you look for a button called zoom or format or aspect ?If you find one then press it repeatedly to toggle between the different aspect ratio ?
Also your tv`s remote will have one of those button.
O.k are you talking about the tv remote or cable box remote or both ?
On the panasonic remote it is called" aspect "
Usually on cable box when you press the zoom or aspect button it will give you 3 choices; standard,stretch,zoom
Set it to standard
On panasonic tv`s, usually you will have 4 choices when you press the aspect button; just,4:3,zoom and full.If you set it to "just" then it should(usually) set the picture to the screen size.
Is your cable box set to send a 4:3 signal or 16:9 ?