ok you need to put the cards in surround
which means 1 video cable coming out of the video card has to be on the second 1
which means no sli but the cable has to be there
then go to nvidia control panel
and click span displays with surround
and test the game should work
also if you dont understand here is nvidia's guide
http://www.geforce.com/whats-new/guides/how-to-correctly-configure-geforce-gtx-680-surround#3