Consider the following scenario. You are running Windows Vista on a portable computer. You connect an external display to the computer, and then you configure the desktop area to extend across both displays. This configuration is known as “Extended desktop” mode. You turn off the computer, and then you start the computer while the lid is closed. Or, you start the computer, and then you quickly close the lid.

When you log on in this scenario, the resolution of the external display may unexpectedly change. The external display may not use the same resolution as was previously used.