The resolution of an external display may unexpectedly change when you log on to a portable computer that is running Windows Vista

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.

This problem occurs because the Transient Multimon Manager (TMM) feature of Windows Vista requires that the portable computer's lid be open when you log on to the computer. If you log on while the laptop lid is closed, TMM is disabled.

To work around this problem, temporarily open the lid when you log on. Then, close the lid if you want.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

For more information about Transient Multimon Manager (TMM), visit the following Microsoft Web site: