The picture on my tv is too big. i have a vw42 l flat screen vizio t.v. we have had it for

Question

i have a vw42 l flat screen vizio t.v. we have had it for several months. recently the picture on it is too big for the screen. so i cant see any of the writing on the bottom of the screen. like for instance, when who want to be a millionaire is on, i can only see the first 2 answers and not the bottom ones. can you please help me as it is driving me nuts and i cant find my owners manual