The very nice thing about far-out video cards is the ability to run multiple monitors off of one computer, which isn’t a new thing, but think of yourself and the pleasures that it would give you, playing your favorite game, watching DVDs (hehe!).
Windows Vista, XP, 2000, ME, and 98, is natively supported so you can display your cool desktop on 2 or more monitors.But let me focus on two monitors. To enable dual display, navigate to the “Settings†tab of the “Display Properties†screen in Windows, and where most people are used to see the controls for one monitor, you will now see two. Those two monitors settings can be enabled/disabled, set to your preference to match the configuration that they physically occupy on your desk. select “Extend my Windows desktop onto this monitorâ€, to allow the cursor freely move from the primary display to the second if it was all one surface. You can move programs, icons, taskbars, and wallpapers onto the secondary monitor and start taking advantage of the increased desktop space. With this setup, you computer becomes more convenient and fun to use.
Personally, I love the extra space it gives me, I can spread my documents easy viewing without having to switch and tab back and forth. and being able to use one monitor for the browser, and the second one is to display my e-mails, instant messaging, Audio/video playback, and another important benefit of dual displays can be experienced in 3D games. As many of the games are now supporting multiple monitors in order to enhance the experience. In a business side of things, dual displays can also be beneficial In being able to view multiple documents at once,
The functionality of dual display is built into just about every operating system available. On the hardware side, is a funny thing. You need to have a pair of monitors (hahaha!). The second thing you have to connect the monitors to the computer, by using a dual-head graphics adaptor, such as the nVidia GeForce 6600 PCIe card. The connectors on this card allow for either one digital and one analog, or for two analog monitors to be connected to the system through the use of just one PCI Express x16 slot. There are also dual-head cards available for AGP and PCI.
For digital displays, one 15-pin VGA connection for an analog display, you can use them as a combo display of monitors by using a DVI to VGA adaptor. some cards offer two DVI connections or two VGA connections. A VGA connection is the 15-pin plugs that has been the default feature connection on computers.
For Notebooks, most modern notebooks feature a VGA connection that can either be used as the primary display or as part of a dual display arrangement with the notebook’s integrated display. But not all notebooks allow for this, as some will only mirror the display onto the attached monitor, so it is best to check the features and specifications before making any purchases.
via [PCExtreme]
It has happened with Vista and is seemingly also being built into 
