There are a couple good sites for finding out how well a game will work on your system:
http://www.yougamers.com/gameometer/10213/
http://www.systemrequirementslab.com/referrer/srtest
I'm guessing you could play on medium settings @ 1280X720 with an acceptable framerate. I have a 9600gt and AMD dual-core cpu and I play with a mix of medium/high @ 1280X720. Perhaps you may have to turn down the resolution a little more, but I'm not sure. Those sites should help you though.
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