Quote from AK100:
...The only way is to have 2 (of the same) PCI Express video cards installed and then you should be able to run 4 monitors. But even that might run into trouble with some machines.
On budget mobos, nobody can really say what the deal is on a 3rd or 4th video card unless they have tested (or if someone else has tested and can vouch for the setup.)
Could be...
1. Installing video card turns off on-board video (may or may not be re-enabled in SETUP).
2. Installed video card works with on-board video.
3. Certain video cards work together, others not.
4. Some computers will run with 2nd video card in x1 slot, some not.
5. Some x16 cards will work with PCI card, but not all.
All depends upon the BIOS.
If you want to be SURE you can run 3-4+ monitors, get a mobo with enough PCIEx16 slots for running dualheads or quads.... and get video cards designed to work together in multi-monitor setups.