What model # is it? If it has the 160w PSU you really can't put much on it, aside from an HTPC card like the 5450 if there is room for a full ended low profile card addition. If it does fit, it will be better than the integrated, but it won't be great, or even good for games. You will be limited to the lowest settings in modern titles to maintain playable framerates.
gonna need a few more details to answer you corectly. provided you have a pci express in your box then yea thats a decent card 9600gt is good. its kind of an older chipset but it'll play most stuff with low-mid settings, but in the hundred dollar range thats gonna be most things
umm comments said people were running em in systems with 200 watt powersupplies.. but i never trust stock powersuplies. if you want ot to last i'd probablu get a good 80 plus rated one if you can find one that will fit