I did it, but I dont remember how. I think it was in the video cfg file. I'll post back later tonight when I get home if no one responds. Its was funky however, as you couldn't move the window, it was just your desktop, and then the game would occupy the upper left corner to your resolution. So you needed to arrange the other windows you wanted to see before starting up the game.
EDIT:
Quick google search refreshed my memory.
Edit Video.scr
Code:
C:\Program Files (x86)\City Interactive\Sniper Ghost Warrior\Game\out\Settings\Video.scr*
*different for Steam.
Set:
to
Although doing this resulted in the behavior I described above. You can probably use
to set an initial window position.