2 graphics cards

The new PCI Express cards can be bridged/joined to each other. Kinda like dual CPU I guess.
But normally motherboards only have 1 AGP slot so if you want a second card it would have to be PCI

I believe it is possible to have two stand-alone graphics cards in the same pc, although i couldn't say how the pc would react. For example, i am sure you could have one in the AGP slot and one in a PCI slot or something and then in Display Properties in windows you would specifiy which to use.

These days though two of the new technologies have been SLI from nVidia and the equivelent from ATI. These technologies allow you to put two PCI Express cards into your machine and have them work together at near double the speed of the single one.

But in your situation i would completely uninstall the old card. If the card you currently have is an ATI then there is a utility on the ATI website that completely removes any trace of the card from your system. It was recommended to me over the conventional methods of hardware removal.

Ace

In theory: yes.
In practice: usually not. Getting two video cards working side-by-side is a bit of a nightmare.
For starters: most cards are AGP at the moment, and motherboards only have one AGP slot. (Maybe some exist with 2, but I've never heard of them)...
Next, if the old one is an integrated card the BIOS will usually disable it completely when you put in any other cards.
Let's say you have a new AGP card and an old PCI card - well, they might work, they might not. I have only seen one PC that seemed happy to use both cards, but every other PC I've tried this in will only use one or the other. One PC would even just randomly pick one at every startup!
If your concern is for dual monitor support, most newer cards are dual-head anyway - VGA and DVI (some also have a TV-out that can be set as a 3rd monitor) - and so with the use of an adapter on one of those you can have dual monitors easily.

1. Why are you getting a new graphics card? Performance, more monitors, etc.?
2. What is your current set up- what slot are you using for your current card and what slots are free?

My one experience with dual graphics cards went like this: I plugged my S3 Virge (ANCIENT card) into a PCI slot my mate's computer (running Windows 98) which had a GeForce3 ti500 in the AGP slot. Worked right off the bat, dual monitors and all. I couldn't test it on my own computer, however, due to the lack of S3 Virge drivers for Windows XP.

Yes it can be done, and it can actually be useful for dual/triple/quadruple monitor setups. You can get multiple cheap PCI videocards and keep your existing AGP or PCIe videocard in your PC. I have done it before, it works well most of the time. Of course, its possible you could have a hardware or driver conflict, but it shouldn't be the case. Cheaper PCI cards will do a fine job at running extra monitors to watch videos, do office work and surf the net. You can't expect much 3D performance from them, but you usually don't need it either, if you keep your main screen plugged into your main videocard to play videogames with.

As far as SLI is concerned, you would need a pair of SLI capable videocards, and two PCI express x16 slots on your motherboard (which you probably don't have, as its not common, unfortunately).

Of caurse you can. I use 1 agp card and two pci cards. The pci cards can give you some error which is mostly a conflict wit the irq's

ive got a 6800 Ultra SLI/256 MB per card, on my PC right now.. so yes its possibly, just make sure you have a Pci-Express mobo.

For SLi, you need an SLi-capable motherboard, which comes with two PCI-E slots. Then you need two SLi-capable video cards, and they must be exactly the same kind. SLi needs to be supported by the application for it to take effect, which is why I recommend......
ATI Crossfire. You need a Crossfire Edition motherboard (also comes with two PCI-E slots), any X800 or X850 based video card, and either an X800 Crossfire Edition or an X850 Crossfire Edition (depending on if your other one is X800 or X850). Crossfire is supported by everything, but I haven't seen the motherboards for sale yet.

Sure, almost everyone in our office has (or had) two cards. I currently just have the one 6600GT PCI Express card, but on my previous motherboard I had a GeForce3Ti200 AGP, and a Radeon 7500 PCI. Useful for a second monitor. Useful for testing different generations of card. Useful for testing cards from different vendors. Useful to test your engine works on a different adapter/monitor than the primary one. Still, personally, I hate dual-screen. Give me one nice 1600x1200 screen and I'm happy.