The traditional view of a "PC"
If you ask just about anyone what their idea of a "PC system" is they will probably list a tower, a keyboard, a mouse and a monitor. While it is true that these are the essential elements of using a personal computer, it is becoming more and more popular to use an alternative setup.
Sometimes two is better than one
It is becoming increasingly more common to see people using two towers with one keyboard, video and monitor. This is accomplished through the use of a KVM switch – as you probably already guessed, KVM standard for keyboard-video-mouse. This is great for people who need more computing power than they can get with one machine. A good example of this would be in a graphic design environment where you are consuming a high percentage of your available RAM and CPU power to run heavy editing applications.
Sometimes you need more room to be productive
For some people computing power is not a huge issue, but they could use more desktop space: enter the dual-screen setup. This allows you to have two monitors that essentially share your desktop. You can drag items from one monitor to another and if you have a long window you want to view, you can sprawl it out across both monitors. This is great when you need to use another screen as a reference or you want a static window that you can always check (with stock symbols, sales figures, etc.).
It's not that hard to do
A lot of people see dual-screen setups and they think that it's hard to do – it's really not. First of all you need a dual-monitor video card. Do not try to use two single-port video cards – you will probably have IRQ conflicts that will keep you from using both at the same time – special software is bundled with all dual-port video cards that allows both ports to peacefully co-exist .
DVI vs. VGA
For some reason most dual-port video cards have one VGA port and one DVI port. I am not saying that dual-port VGA or dual-port DVI cards do not exist, but I have never seen one. This can be kind of a pain because you might have two VGA monitors or two DVI monitors. Do not worry – there is a solution. You can easily find a DVI-to-VGA adapter or a VGA-to-DVI adapter from just about anyone who sells you a video card. Be aware that if you have two DVI monitors that your DVI signal will be downgraded to analog, but the quality loss is almost unnoticable unless you have a huge monitor. Also, using a VGA-to-DVI adapter will not upscale your signal to a digital signal – it will pass an analog signal through the DVI port.
You will need to install included software
Regardless of where you buy the card from there will be some software that you will have to install to get your new setup to work. As I mentioned earlier, this will resolve any IRQ conflicts that would otherwise align and give you some cool options for your desktop such as specifying which monitor should be the right-side of the desktop and which should be the left.
Be sure to uninstall your old card first
Whether you choose to use an AGP video card or PCI, you should definitely remove your existing video card first (and disable any software related to the old monitor). This will remove the possibility of a driver conflict and make you and the computer much happier in the long-run.