How to force a resolution on Windows 7

In Device Manager, try manually installing a driver for your monitor. Right-click Computer, then click Manage. Expand Monitors, then right-click your monitor and click "Update driver software...". Click "Browse my computer", then "Pick from a list". Uncheck "Show compatible hardware" and select the "Digital Flat Panel" for your monitor.

Check the NVIDIA Control Panel, you should be able to add a custom resolution and enable it from there.