it used to blasphemer,.. but since Forceware 62, that hasn't been an option anymore
these days you have to set it as dual view, extend horizontal, extend vertical. or clone (clone means both monitors show the same)
extend means it makes it a wide screen
vertical is if you have 1 monitor on top of another
and dual view is to allow 2 seperate views at the same time
dual view is slower in games though