"...messed around with display settings" but you didn't tell us much else.
If you right click on the desktop and select Properties then the Settings tab what resolution is shown? Does it match what your monitor is capable of - 1680 x 1050? If not try setting it to that screen resolution.
Monitor had been working properly until just recently. Its as if the screen itself is not big enough for the display. I've messed around with display settings and have even tried to download the driver for this monitor. The download stops and displays a message that the computer is not authorized for that download. Running Windows XP, which is the same computer that the monitor had been working correctly. Any help would be greatly appreciated.