nvidia fsx stretched screen

[theedge123]

Hi all can someone help....
Im trying to stretch my fsx cockpit across 2 screens. I run a nvidia gtx470 and a 260 but just for this im running 2 screens from gtx470. I have got fsx cockpit in middle of the 2 screens inwhich works fine but as soon as i start to stretch fsx to fit the 2 screens my right screen inwhich is number1 screen starts to go black from right to left and the more i try to stretch the screen the bigger the black page becomes to a point where the hole right screen is black. If i unstretch the screen the black page gets smaller inwhich allows me to see more fsx on number 1 right screen...
I Know this can be done with a radeon graphic card where you can stretch fsx across 2 screens but can it be done with a nvidia? Ive youtubed this and followed but i cant get the black page to go
Any ideas anyone
Thanks
Dave