For a computer installed with the Microsoft Windows Vista Service Pack 2 (SP2) operating system, when the user turns on presentation settings through the following procedure, and then attaches the computer to an external monitor, all the presentation settings the user made will be lost.

The user can turn on presentation settings by doing the following:

1. Click Start, Control Panel or Start, Settings then Control Panel.
2. In the Control Panel Classic View, double-click the Windows Mobility Center icon. The Windows Mobility Center window opens, presenting a collection of menu options.
3. Locate the Presentation Settings section, and click the Presenting icon. The Presentation Settings window opens.
4. Change the presentation settings as desired.
5. Click OK to turn on the settings.
   

This is by design of Windows Vista SP2.

• All ThinkPad systems
• All Lenovo 3000 Notebook systems
  
  

You can find a work-around here:
http://support.microsoft.com/kb/971754