I have a 23" Hannspree HF237 LCD monitor 1920x1080. My graphics card is an xfx 5770. the problem is that when im using the computer the screen is not spread to the full size and it wont let me manually adjust it in the settings but when i play a game it goes to the full screen.
Try updating the drivers for your GPU and see if that fixes the issue. If not, take a look at the settings within the monitor itself. There should be some sort of auto populate option that you can enable to utilize the whole screen all of the time.