right click on desktop, open the nvidia control panel, choose sli and physx thing on the left hand side and tick the maximise sli performance thing.
Is the sli bridge connected?
Weird, it has surround options where normally there would be SLi..
What's rest of the spec of you pc?
Did you try actively removing the old drivers before reinstalling the new ones like SuB suggested? Sometimes when you just overwrite old drivers with new ones, files get left behind which may be causing the problem.
Try using Driver Sweeper: http://www.guru3d.com/content-page/guru3d-driver-sweeper.html
I feel a little nOOb but then again I did work it out myself.
Don't put your sound card in a GPU slot
Cheers all.
Were you putting the second graphics card in a slot that was only wired 4x or something then?
Sorry but I'll just say one word and I'm sure you can understand and take it lightly...
LOL!