Short answer: Restart your computer.

Explanation: I have two monitors that I was trying use with my computer, and I encountered a particular problem. I’m running Windows XP Pro SP3 with NVIDIA graphics. I tried to set up the monitors in a primary/secondary configuration, allowing each monitor to have a different resolution, and my task bar to fill one screen. I had a problem because despite the help literature describing the option, I had no ability to select “Dualview”. After searching the web for a solution, some more brutal than others, I tried a simple one. It was suggested that I restart my computer. The reason being that the NVIDIA control panel or my operating system can’t detect both my monitors at a low level unless the operating system is started with both of the monitors connected. Since I didn’t plug in the monitor until after the system was up and running, it hadn’t been started with both monitors. Restarting the computer fixed this problem because it allowed the operating system to detect both monitors at start up.