Find the galciv2.exe file
Drag it to your desktop
Create shortcut
Right click on shortcut to get the properties
Under properties, Change the target by adding a space and a w to the end of the target, the space between the " and the w is important
The target should read something like this.
"C:\Program Files\Stardock\TotalGaming\GalCiv2\GalCiv2.exe" w
If your windows desktop is the same size as you Galciv2 resolution, you may not see any difference, but you may notice that you may more easily use alt-tab and the windows key to switch between programs.
If your galciv2 res is smaller than your windows desktop you can move the galciv2 window around.
I play in windows mode at the same resolution as my desktop, as it makes swiching in and out of Galciv2 easier.