Can I Add a Second Monitor to My PC? - dummies

By Dan Gookin

Certain editions of Windows can power two monitors. All you need to complete the picture are two monitors plus two display adapters or one display adapter that can handle two monitors.

The easiest way to tell whether your PC has this ability is to check the spot in Windows where screen resolution is set. In Windows 7, it’s the Screen Resolution screen. In Windows Vista and Windows XP, it’s the Display Properties dialog box. When a second monitor shows up in either of those places, your PC’s display adapter has the ability to use two monitors.


To use the second monitor, select it in the Screen Resolution window or Display Settings dialog box. What you do next depends on your version of Windows:

Windows 7: Choose an option from the button My Multiple Displays. Choosing Extend These Displays creates one large desktop across both monitors.

Windows Vista: Choose the option Extend the Desktop Onto This Monitor.

Windows XP: Choose the option Extend My Windows Desktop Onto This Monitor.

The taskbar shows up on only one monitor. To see which monitor is which, click either the Identify Monitors or Identify button.

The option you choose in order to set the main monitor (the one on which the taskbar appears) is titled differently, depending on your version of Windows. To switch main monitors, click the monitor that you want to be the primary monitor and then choose one of the following options:

Windows 7: Make This My Main Display

Windows Vista: This Is My Main Monitor

Windows XP: Use This Device As the Primary Monitor

Every monitor has its own resolution and color settings. To change the settings, choose the monitor from the menu in the center of the dialog box and then set its resolution and colors. Changing the resolution changes the monitors’ relative sizes in the window. You can then drag the second monitor around to adjust how they relate to each other.

Drag a window between the two monitors to see how their positions relate. In fact, you can use either the Display Settings or Display Properties dialog box for that test.

Click the OK button when you’re done arranging the dual monitors.

  • The easiest way to set up dual monitor hardware is to buy a dual monitor adapter. It comes in VGA and DVI flavors.

  • A display adapter with a digital connector can drive two VGA monitors. You need to purchase a DVI-to-dual-VGA adapter to set things up.

  • Most laptops have the second-monitor ability built in. They can easily use external monitors and video projectors for making presentations. See Book III for more information on troubleshooting laptop computers.

  • To swap the Windows Vista Sidebar to the other monitor, open the Windows Sidebar icon in the Control Panel. In the Windows Sidebar dialog box, choose the monitor number from the menu by the item titled Display Sidebar on Monitor.

  • Changing the main monitor doesn’t change its number. To change the numbers, you have to swap the monitors’ display adapter connectors on the PC.

  • Do not remove a monitor while the computer is in hibernation. Doing so can prevent the logon screen from showing up when the computer restarts.

  • Monitor mirroring occurs when you display the same image on both monitors.