Only part of the computer image displayed. What should I do?

• Make sure the correct Input Signal is selected in the Video menu.
  
  Make sure your computer's resolution doesn't exceed UXGA (1600 x 1200), and the frequency is supported by the projector. If necessary, change your computer's resolution setting as described below.
  
  Windows: Right-click the desktop, select Properties, click the Settings tab, and select a different resolution.
  
  Macintosh OS 9.x: From the Apple menu, choose Control Panels, then click Monitors or Monitors and Sound. Select a different resolution.
  
  Macintosh OS X: From the Apple menu, choose System Preferences, then click Display. Select a different resolution.
  
  You also may need to modify existing presentation files if you created them for a different resolution. See your software documentation for specific information.