Screen resolution suddenly limited to 1024x768 and under

So today when I booted up this computer the screen resolution had suddenly changed to 1024x768. When I went to change it back (my monitor is about 20 inches in size, so that resolution looks really bad) I found that I couldn't get a resolution higher than that, and the only other resolution available was 800x600. I've been trying to fix it-I restarted, tried to do a clean boot (which didn't do anything when I first restarted so I stopped trying), updated the nvida driver to the latest version, but nothing works. I thought it might have something to do with a game, because I got Fall of Cybertron just yesterday, which didn't cause any resolution problems when I played it yesterday but it could have been the culprit, but they're all limited to the same resolution settings too.

In case it helps, I'm running the 32bit version of Windows 7 and this is what my screen resolution menu looks like.

try increasing the resolution using the Nvidia Control Panel

That helped me a lot, thanks. I managed to get it to a better looking resolution through mucking around with custom resolutions. I haven't managed to get it to the resolution that it used to be, though. I thought it might have something to do with the drivers for the monitor. My monitor's a Chimei CMV 221D, and apparently its native resolution (which I'm assuming is the best resolution and possibly what I had originally, given the dimensions of screencaps I took with it) is 1680x1050. But none of the available drivers for the monitor that are on my pc have this resolution; the closet is 1600x1200.

I'm beginning to think that it's a hardware issue.