Cannot get 3rd monitor to enable

[frustratedwin7]

I have a dell studio xps 7100
running a MSI r5670 graphics card
Ati CCC 10.8
Windows 7 Ultimate

Monitors = 1 Display Port, 1 DVI, 1 HDMI
Bios on A03 latest version

I cannot get the 3rd monitor to enable. When i choose enable it says unable to save display settings.

I need to enable the third monitor. But am unsure of what to do now

 

[alphanumeric]

You might have to check the specs for supported resolutions very closely. I've seen some video cards where the maximum usable resolution shrinks the more monitors you use. It may be that your three monitors combined exceed the maximum resolution that card supports. If that is true you will have to lower the screen resolution on your first two monitors and then see if you can add the third.