For that setup core 2 and 10600 and 320gb HDD and older Video Card, very weak compared to current. I would say that since it is not upgrade capable to the core 4 or higher you will get maybe $100 to $150 for it. And that is if you sell it to a consumer. A shop will buy it from you for about $35 or maybe not even be interested.
What OS do you have on it? Probably windows 7 or before?