The answer is don't run in full screen mode. What you are experiencing is the equivalent of watching the full screen version of a wide screen movie. Play in a window shaped like wide screen and you'll see the equivalent of the the letterbox version.
The whole reason is your moniter's aspect ratio. When you're playing in windowed mode, the aspect ratio, according to that picture, is approxametely 16:9 aspect ratio, which is more rectangular. Your screen is too narrow, so it can't fit most of the item. If you were to use a moniter with a more rectangular aspect ratio, like 16:9, then this problem shouldn't persist.
There isn't a software-based fix for everything. Getting a new moniter is all I can think of, unless you do something to add black lines on the top & bottom of the screen to simulate a different aspect ratio.
Have you tried going into profile settings and checking Resolution. I know you said it looks ugly, but it's the best it can look like with a old standard-issue Windows monitor. Before I got a BenQ, I had a 1680x1050 by HP from 2009.