Update to the latest ATI driver and Catalyst Control Center (optional) – This should be straightforward if you own a desktop, but on my Dell laptop ATI’s installers won’t upgrade your drivers (or even install new ones after you’ve uninstalled the old ones — apparently only the OEM drivers will install). Anyway, Ruud Ketelaars has developed “Mobility Modder” which can tweak the installation files so that you can upgrade your laptop’s ATI drivers. You can find his software and instructions here (scroll down).

Add the max resolution of your monitor to the available options:

1. Open ATI’s Catalyst Control Center (CCC) by right-clicking on your desktop and clicking on the “Catalyst Control Center” option.
2. Make sure you are in advanced mode (lots of menus on the left side).
3. One of the menu options on the left side will be something like “Digital Panel (DVI) 2″ and will probably be listed just under “Notebook Panel Properties 0″ if you are using a laptop. Click on the “HDTV Support” submenu of the “Digital Panel” menu.
4. Under “HDTV Support”, click the checkbox next to the resolution and refresh rate which you want to enable for your monitor. For my monitor, this was “1920×1080p50″ (50Hz).
5. Click “Ok.”
6. Open Display Settings like usual and you’ll be able to choose the new resolutions you enabled (right-click on the desktop, choose Personalize, then Display Settings)