In Microsoft Windows-based operating systems, users can use multiple monitors with one computer. This can be useful for users who run multiple applications at once and need to view them all at the same time. Once you have two monitors connected to your computer (see specific instructions included with your monitors for help, if needed), switching between them, setting dual-display and extending the desktop are quite simple.
Switch Between Monitors
Open the Microsoft Display utility. To do this, go to Start > Control Panel > Appearance and Personalization ("Appearance and Themes" in Windows XP), and then click on "Display." (The dialog box should automatically open in the "Settings" tab. If not, open it manually by clicking on it.)
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Click to open the monitor drop-down menu and then click to select the monitor you wish to enable for use as your primary monitor. If necessary, click to deselect the other monitor.
Click "Apply." Your settings will now be put into effect. If your changes show up as you hoped, click "Yes" to confirm the operation. If not, click "No" to undo the changes and retry. Once confirmed, click "OK" to exit the dialog box.
Dual-Display & Extend the Desktop
Open the Microsoft Display utility (see previous section).
Click to open the "Display" drop-down menu to view the list of monitors. Select the monitor you wish to duplicate or extend the desktop onto.
Check or un-check for "Extend my Windows desktop onto this monitor." If left unchecked, the content on the primary screen will be duplicated on the secondary screen. If checked, the content on the primary screen will be extended to the secondary screen to act as one giant screen.
Click "Apply" and then confirm your settings in the confirmation dialog box. (If the settings do not appear as desired, click "No" and then tweak the settings.) Click "OK" to exit the Display settings.