Any GPU will work with it, so long as your power supply and case can support it. Bear in mind even a GTX 750ti will be bottlenecked by such and aged system. But if you do it, that would be my suggestion.
It should only be slowed by about 16%, regardless of that your system will be the biggest cause of your games not running efficiently. DDR2 and outdated microcode are really what's getting you. Get a decent graphics card now and bottleneck it or wait until you have the cash to build a new system all together. Either way you will still need a new GPU to keep up and the 750ti is a great budget card.