To hook up two monitors to a single display source, you need to connect them to graphics card that supports multiple display outputs via VGA, DVI DisplayPort or HDMI cables. Once the monitors are connected, you can modify the display settings in the Screen Resolution section, accessed via Control Panel.Continue Reading
Look at the back of your computer case in the area where the graphics card is located to determine which display outputs it supports. Look at the back of your monitors to determine the types of display inputs they support. Use the appropriate cables to connect the devices to the graphics card. If you connect the devices while the computer is turned off, Windows 7 should automatically detect them.
Click on the Start button, and select the Control Panel option. If the Control Panel elements are displayed as categories, click on Hardware and Sound, and select the link labeled Connect to an external display. If the elements are displayed as icons, click on Display, and click on the link labeled Change display settings. Both of your monitors should be displayed and marked with numbers 1 and 2. If not, click on the Detect button.
In the drop-down menu next to the option labeled Multiple displays, select Duplicate these displays to have both monitors display the same content, or select Extend these displays to have both monitors serve as a single display. Click on the monitor you wish to use as a primary display, check the box next to the option labeled Make this my main display and click OK.