I think I see your problem.
:P
It's actually not as bad as it sounds. Thing ran as fast as hell despite it's processor.
Not on games of course, but everything else.
But still, my dad's computer is a dual core @ 3.1GHz with a 9400 GT and can barely run Fallout 3.
I don't think an 8400 GS can run it very well, probably on lowest settings.
Maybe.
EDIT: And just to clairify, I don't have that computer anymore. My new one is much better, I custom built it myself.