system

I`ve got ms combat flight sim 3 and I would like to improve the performance. It runs reasonably well but stumbles in places, such as when firing guns and also when I crash the plane. The scenery is also pretty basic. My system is win 98, pentium 3 866 processor 512 mb ram and 32 mb g-force card. My question is wether an upgrade would improve anything such as win xp or a new graphics card or a better processor?
...............slinky................