The only thing is that your pc's motherboard only supports agp 4x speed which the card will only run at that speed. It will run but at 4X. That video card would actually run cod2 good if it was at 8X speed but 4x should be fine for you and the jerky is due to if the video settings are turned up to much for the whole system. If you get it it will automatically pick out the optimized settings for your system if it is still kinda choppy just lower the settings abit. Like I said that is the only choice you have.
If you had a new motherboard and case you could have a better video card depending on what you chose, agp 8X or pci express for the graphics slot.
If you do ever get a new pc make shure it has pci express on the motherboard and the powersupply is high quality and atleast a true 400watt -500watt.