Ok I was just wondering if it is possible to run dual monitors with my setup?

I was thinking of using my 2x8800gt running in SLI for my gaming and using the onboard NV 8xxx graphics card to run my second monitor.

Does the 3rd card need to be from ATI?

Ok, tested it last night. I now have 3x 8800GT (g92) on my M3N-HT Deluxe and it is working perfectly! I have PCI-e slot 1 and slot 3 SLI'd and PCI-e slot 2 running all by itself.

Just in case people need to do it:
1. Used Driver Cleaner Pro (freeware) in Safe Mode to wipe all the drivers.
2. Installed all 3 cards independantly (none SLI'd)
3. Rebooted into normal Windows.
4. In Windows, installed the most current driver 175.16
5. Rebooted.
6. Activated all 3 monitors in Display Settings
7. In Device Manager, I disabled the middle PCI-e GPU.
8. Rebooted
9. In NV settings, turned on SLI for PCI-e slot 1 and 3
10. Rebooted
11. Enabled GPU in slot 2 in Device Manager -gave me an error saying that the driver was out of date? I hit ok but it still enabled it.
12. Rebooted
13. In Display Settings, I moved Display #3 (since that is what PCI-e slot 2 is registed as) next to Display #1 (Main SLI'd monitor).
14. Applied, OK'd
15. DUAL MONITOR with SLI enabled!!!

I did all the necessay test to check for SLI (3dMark 03, 05, 06). All gave me the same score when I had my SLI without the 3rd card.

Also, Riva Tuner will show you incorrect information since this is a work around. It shows 3 GPUs installed. 1 of which says SLI enabled (2 GPU) and the other 2 will not show that SLI is enabled.

If you OC your cards, it will be confusing since all 3 are 8800GT's. Since I have them all on WC, I set the primary (SLI'd) card to 745/1050 with the shaders linked. This will also set the 2nd card (which you cannot change the setting on) that is linked to the primary card via the SLI link to the same clock setting. And the card with the 2nd monitor the same clock setting.

All this was done with Windows XP x64!