Aspect Ratio Incorrect

I cannot get the aspect ratio to show the entire image when I am watching a movie. I have a 26" Vizio hooked up via hdmi cable, and have tried messing around with both 720 50Hz and 720 60Hz. I know my TV is capable of these settings, it just doesn’t seem to work correctly. Also, when I try to switching between widescreen and normal, it still chops off either the sides or the top and bottom. The aspect ration on my TV is 16:9, and the video I know for a fact can fit in the screen at 720, and even if it couldn’t, there would just be black bars on the top and bottom of the screen, which I would much prefer to the picture being chopped off.