Depends on the resolution you want and whether you want both to be dvi
Most current cards have at least one dvi port and one analog port. So if you have sufficient video memory you could run one monitor off of each port. Some cards have multiple dvi ports (or analog)but you can have multiple cards. Multiple cards can be a hassle. They must be compatible to some degree to coexist.

IMO use what you have if you can. If not look into a single card with multiple monitor support. You will probably want at least 512mb of video ram (on board) and dual dvi ports.Some of the ATIs are reasonably priced. For CAD work I have an Nvidia Quadro FX 4500 and I don't want to mention price but....OUCH! At home I have an ATI X1600 PCIE that does the job well for about 1/5 of the cost.

Edit: by the way, to initialize your second monitor go to the Display Properties > Settings page and click on each monitor shown (1, 2) and below that select one for primary and choose "extend..." for the other.

I would not say that is an idiot question. I struggled finding info on it was well. I did not want to buy the wrong card and end up just wasting time and money. Setting it up is super easy, and once you go dual, trust me, you will never go back. It rocks. I bought an EVGA GeForce 7600 GT KO (newegg.com). It has dual dvi outputs. It also came with two dvi to vga adaptors. Setup could not have been easier. You simply put the card in, power up and follow the few steps of instructions. I have had it installed on 2 dells, both no older than 1 year. I don't know what you run, but again, I had no problems.

I am not into games, I use it for work. For spreadsheets, word documents, surfing the net, and, of course, the stardock suite of products, it works great. No problems, no complaints. I would buy it again for sure.

Hope that helps.

I have two monitors on a Geforce FX 5200.
As JavaFiend said, once you go dual, there's no going back to a single monitor.

thanks Lantec, you answered my question perfectly. My card is a GeForce 6800 GT with 256 memory. It has dual analog ports, but do you think the 256 memory will be an issue?

It shouldn't be an issue depending on screen res. color depth and assorted rendering settings. Here's a link to give you an idea on Video memory WWW Link

thanks again. That article was very informative. I feel pretty confident running 2 monitors with what I have.

I set up dual on a Radeon 9600 w/256 just days ago, RPGFX ...works extremely well, and I'm happy with it.

A good friend provided me a link to UltraMon too. It's a handy little app that will give you all kinds of extra tweaks etc, to get the best out of your setup. Not free, but it does have a trial period, so you could at least give it a whirl. [Google it]

Upon installation, it detected that I had WindowBlinds installed and told me there might be 'issues' ...but I'm yet to find anything borked.

All that extra screen real-estate is a huge plus!

As I remember the main issue is the title bar buttons that you can add. As long as you don't use them there's no problem.

Yeah, they can't be skinned or moved. (The titlebar button won't show up on per-pixels frames even you try to use them)
And the taskbar on 2nd monitor won't be skinned if I remember correctly.

I ran dual monitors on a 5600LX 128MB for years and never had an issue. You should do just fine. Now i have 2 7800Gt 256MB cards and ran up to four monitors and never had an issue.

I'm running them just fine. No issues at all. Except that one of my brand new monitors has a dying pixel... thanks for all the info folks!

Happy new year!

Take it back, I personally wouldn't stand for that. I took two back before I got the one I wanted.

I intend to. But they are all out of them right now. As soon as I see them in stock, I'm going to.