I'm thinking of setting up three screens on my open day display to make it stand out, so i stole mikes screen and put in a pci graphics card and hooked it up. Initially the third screen (PCI card) didnt work, but after a quick google i found that all that you need to do is set the PCI card as primary in the BIOS. Then using Ultramon i set it up to give an extra wide desktop.
As you can see the third monitor wasnt as good as my other 2 and so the resolutions are different giving a big black bit, although you dont see this on the screen, all the windows are just bigger on the third, older screen.
If you have the money and are planning something like this i cant stress enough that you get 3 identical monitors, it would make everything so much easier, and if you can get 3 TFTs then your desk would thank you as well.
Ultramon is the ONLY software you need for Dual or triple or up to 10 screens, as well as wallpapers and screensavers to stretch across your whole desktop.