Put a new video card (PCIe) in my fairly old PC, it had 2 outputs so I dug an old monitor out and set up dual displays.
Its excellent, so I’m thinking, if I buy another monitor can I use my old PCI video card to run 3 monitors?

I doubt it. Have just gone over to a dual monitor setup at work. Unless you can somehow run the cards in tandem ( I think you can with some of the high end Nvidia ones), but I dont think the PC can run more than two monitors.

Probably not like that but a guy I work with has a 3 monitor set up and he doesnt have 2 video cards in SLI or Crossfire configuration. There are USB adaptors you can buy that might do the trick if your desperate though?

Some of AMD cards can run up to three or six monitors http://www.amd.com/us/products/technologies/amd-eyefinity-technology/Pages/eyefinity.aspx

You can add an older PCI card and run a third monitor, You can add another PCI-e card if you have more than on PCI-e 16x slot and run another 2 if you wanted. I have 4 on mine with 2 PCI-e cards not running SLI.

You should be able to – but remember, stick to the same brand.

Ati + Ati, or nVidia + nVidia.

I’ve got 4 monitors at work ( 4 x 24″ ).

http://www.realtimesoft.com/multimon/gallery_browse.asp?date=desc&nummon=true&mon=desc

I “need” that set-up. Purely to wind folk up. 🙂

Most of us at work run two monitors but the machines are fairly high end cad stations so have nvidia cards with dual digital outputs.

use some usb=>vga converters in work – they work ok, just not for something with high updates

figure out how to use the windows extended desktop and you can run 3 with the existing hardware

plug in extra monitor, go to display properties, click on 2nd monitor in the window, then check the ‘extend my display on this monitor’ box, then fiddle with the settings to get the right resolution

then right click on the desktop and do ‘graphic output’ then ‘extended desktop’