im have a rotated monitor, some games run fine and full screen. others seem 'pinched' and have a black border on the sides. the 194x games for example. running directly from mame32 fixes this.
while run a game, press the tab-key, at the following menu bottom, here you have options for display,
i think, one solution is, you have activate "bezel" and the bezel file is miss ... ( maybe )