Kosti, dystopic and all I Have found the answer
Full screen or windowed dual monitor with anti Anti-Aliasing and smooth cut scene playback.
You need to set the display options in the relevant graphics control panal not in Properties/settings.
The only drawback it that the desktop stretches across the whole 2 screens and all windows maxamizes that size.
So it has to be set back after.
You can set GalCiv2 to any res you like in game and the settings stey put.
I suggest that if you have a nvidia card that you check to see if settings can be saved as a shortcut.
I will be looking at my ATI control panal and let you know. First though another game.
Before I go. This approach will work with quite a few games so I have read but some will just resort to mirroring the monitors.
I tried it with Rome Total War which I have just been given (Looks great) and got the mirroring, It did recognise the wider resolution of the desktop but when selected just stretched the screen to twice its width.
Porky midgets make very funny looking warriors.
A full step through guide for setup in nvidia and ati can be found here
Link
Hope this helps.