sli and xfire only support one 3d program running at one time. the new drivers only allow you to use one monitor for 2d and the other for 3d. they do not support 3d in both monitors.

there are curtain reason that you would want to run 3 monitors. one of them is a more realistic gaming environment, e.g. racing games look fantastic with the increased screen size. 2400x1800 up to 3600x1000. in order to be able to display 3600x1000 you would need to run 2 vid card in sli or xfire or turn the detail down, but that defeats the purpose.

3 video cards for 3 monitors is another solution