SS, your major problem is obviously the graphics card. With 4 MB ram you are not (!) able to get a frame rate you are interested in. Can you upgrade to at least 8 MB or, even better, 16 MB.
See that your harddrive is defragmented very regularly as it is (compared to the requirements these days) also not the biggest one.
To make it worse, your CPU is a bit slow to handle all the fancy stuff in "real" time.
Now that I have not left any good hair on your system, please get me right about my words.
You have a real nice system which will suit you for a long time to come but, if you really need all the speed and frame ratios others are talking about, well, than you need to think about a serious upgrade.
In 1982 Bill Gates said, after the AT-machine, the then 80286 with 1 MB ram was born, that this would be enough memory for all solutions and software to come. Well, he was wrong and he works hard to show this to us all. By the way, the said machine was running with 8 MHz speed.....