I guess you know this, but if not just right-click anywhere on the desktop, (in Windows 7, poss Vista too), choose, 'screen resolution', then if you click on the box 'screen resolution' you see a slider which you can set up how you like.
I have found that all graphic adapters and all (2) of my monitors, don't have all the resolutions, and only when you get the correct Graphic driver, will you be able to get the highest resolution.
If you bought the Graphic card new, and it had driver disc included, my experience is that it will be out of date. You have updated it and that should be ok, but if you want to scan your pc with a third party program, try;
www.drivereasy.com
Download the free version of the program and scan. See if the driver is what you have installed. Also it might tell you about the monitor driver too.
Note that the program
can download the drivers for free, but they are at a rate of about 15 kb/s, so unless you have all day to spare.... Of course you can write down the info, and go to the 'right' site to get the actual driver, if needed.