Information about the case would be good too.. is it a standard atx case or some slimline custom job from dell/hp/etc? Motherboard and case are really all I wanted to know about. And btw I hope that pc came with that psu... those things are $4.99 used on Amazon.
You should really, really think about getting a better psu before sticking a video card in there. You don't want to overload it. If luck is not on your side it could end up taking more of your pc with it on its way out.