I know that in Unreal 2 it has built in monitor settings for dual. But it works only by setting the proper dual monitor resolution i.e. 2048x768.
Do what marq said and look into the unrealtournament.ini file that has the monitor settings and set to your desktop resolution.
I think it may look like this:
FullscreenViewportX=1024
FullscreenViewportY=768
Change those to 2048 and 768 and give it a try
