SETTING YOUR SCREEN RESOLUTION
Your screen resolution, also known as monitor resolution, screen area or display area, is set by your system software.
(Show me my current screen resolution.)
To change your screen resolution in Windows Vista and Windows 7, from the Start menu, select Control Panel: Adjust screen resolution (under Appearance and Personalization), then drag the "Resolution" slider.
To change your screen resolution in Windows XP, from the Start menu, select Control Panel: Appearance and Themes: Display: Settings. For earlier versions of Windows, from the Start menu, select Settings: Control Panel: Display: Settings.
To change your screen resolution in Mac OS X, from the Apple menu, select System Preferences: Displays: Display. For earlier Mac versions, from the Apple menu, select Control Panels: Monitors and Sound: Monitor.
Higher resolutions are capable of displaying sharper pictures if your system supports enough colors. For best quality, set your screen to display as many colors as your system will support at the resolution you choose.
For more about picture quality, please see Saving and Displaying Desktop Pictures.