Only way would be to play in Windowed mode to make full use of the resolution. Besides, GW is very friendly on resources anyway, I've been playing two accounts on dual 1366 monitors on my notebook.
If you are using dual monitors, is GW being played on the "primary" monitor?
Does Windows recognize the monitor properly - that is, does it list the actual name of the monitor, or does it just say "generic PnP"?
Anyway, this sort of problem is usually the result of Windows not properly recognizing the monitor and therefore, GW doesn't know that the monitor can do 1440x900.