How to set up two monitors
Ray Raulerson asked about running a computer with two monitors.
For years, I was quite happy with one monitor. I would see other people working with two of them, and it struck me as a waste of desk space and electricity. Three monitors looked like they would flap their wings and fly away.
Then, one day I was working with my closed laptop in its docking bay, and my eyes on my external monitor. On a whim, I opened the laptop and got a second screen. I've been a two-screen user ever since.
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Chances are that your graphics subsystem can handle two screens. But the issues are different with desktops and laptops.
Desktops: Pretty much all modern graphic cards support two or more monitors--at least all of the ones I've seen. Your motherboard's built-in graphics may also support both, but that's not quite a guarantee. Check the back of your computer to see how many video ports you've got. And then, just to make sure, check the manual.
Laptops: These all have separate VGA ports, and often HDMI or DisplayPort, as well. Plug in a monitor, keep your built-in screen on, and you've got two.
But you need more than the ability to plug in two monitors and send signals to them. You have to tell Windows how to manage both monitors correctly.
The following instructions apply to Windows 7. For Windows 8 setup, see How to set up multiple monitors In Windows 8.
If Windows only appears on one monitor, or if the two of them aren't working the way they should, right-click the desktop and select Screen resolution.
The resulting dialog box provides more than a way to set pixel's. The Multiple Displays pull-down menu allows you to control how the two screens work together. I recommend Extend these displays.
Once you've selected that setting, you can tell Windows which monitor is on the left or right by dragging the graphics at the top of the dialog box. Get this wrong, and scrolling the mouse will be very confusing.
The Make this my main display option controls which monitor gets the taskbar and Start button. If you don't see that option, the currently-selected monitor is already the main one.
You can also control many of these settings by right-clicking the desktop and selecting Graphic Options>Output to.