The Three main ways to Setup Multiple Monitors
1) You can buy a pre-manufactured multi-monitor computer. The best place to purchase a
multiple monitor computer is at:
Multi-Monitors.com. They carry a multi-monitor computer line called
SUPER-PC that can support from 2 to 12 monitors.
Multi-Screen Computer Systems
Multiple Monitor LCD Displays
2) You can get a
USB to VGA Adapter, or
USB to DVI Adapter that will allow you to add an extra monitor to your computer
via any USB2.0 Port. You can also add multiple extra monitors by using multiple adapters. This is a great option for viewing
documents, surfing the web, using Microsoft Office and many other business tasks. This is not a good option for intense
graphical situations such as HDTV, Blu-ray, Gaming and 3D / CAD Workstation applications. For those types of scenarios,
it is highly recommended that you purchase a high-powered multi-monitor workstation or a
Matrox Dual or Triple Head2Go.
Multiple Monitor Adapters
3) You can replace or add an extra video card to your existing computer, depending on how many monitors you wish to support. Although this sounds easy enough, this is a rather complex solution for a beginner, especially when trying to find a compatible graphics card. For this reason, I am going to write an entirely seperate post on that topic and will link to it here, very soon.
Multi-Monitor Graphics Cards
Once you have your multiple monitor system set up and ready to use, you will need to enable all of your monitors in
your “Display Properties” Control Panel. Here is a great link to a complete and animated walkthrough of how to enable
your multiple monitors in Windows.
How to Setup Multiple Monitors (Instructions)
This is what it will look like when you are done:
Multi-Monitor Video Demo 1
Multi-Monitor Video Demo 2 
Microsoft Windows (other)