According to the documentation for your monitor, it's native resolution is 2560x1600. You run your desktop at that resolution, so that is good.
However, you stated that "...NVIDA control panel says that the native resolution for this monitor is 1280x800...". This may be part of your problem. I would suggest going into the NVIDIA control panel and trying to change that setting (from 1280x800 to 2560x1600).
Your documentation:
http://support.dell.com/support/edoc...Specifications
In addition, you stated that your conf file looks like this:
[window]
width=1600
height=1200
ColourBits=32
DepthBits=24
StencilBits=8
ChangeScreenRes=1
FullScreen=1
DrawIfNotFocused=0
EnableResize=0
EnableClose=1
SaveAspect=1
Use3Renders=0
Well, that is 1600x1200. You need to manually change that to 2560x1600. When you do that, start the game. Do not make any other changes in the Set-up screen or you will lose those settings.
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