Your RAM is a bit low, your graphics card is low end and your CPU is a bit old. Everything on your system is old(CPU), low-end(Vid card) or barely cutting it(RAM) which provides ample opportunity for a bottleneck. So, since you have a P4 Mobo, wait a little while and buy a new system and keep the price within reason, ~200 for a vid card, ~150 for a mobo, etc...