Screen Size Problem

[VitaNex]

I have a real urgent problem theat needs to be answered, whenever i play a bluray movie on my sony player the previews are in a smaller size on the screen but when the bluray movie starts it is in normal size and fits my tv screen. But when i try to play a regular movie on my player it is all in a smaller size such as the previews and is really starting to bug me. i have no idea how to fix this and need an answer.