it has three fans cooler master heat sink,and has windows 7 professional,the processor speed is 3.30ghz
That's helpful. I'd put your rig up for around $400, and see if you get any takers. If not, lower it a little bit; my guess is it might sell closer to $300...used, average PC stuff isn't super desireable. You could also try parting it out and selling the pieces separately if you don't have any luck. You've got some good things going for it (decent PSU, CPU, and SSD), but the graphics card is lacking so if someone buys it they will probably be buying it to upgrade it.
And who knows, maybe you'll get more than you think. Good luck!