i'am running sof on a 2.0ghz celeron , 256mb kingston ram , 80gb 7200rpm , intel 82845g 64mb card which is lot more than required.. but still the game lags at certain places.. the frame rates are good but still it lags .. like during cut scenes its a h*ll , then while firing e.t.c

A very late response, but... I bet your video card is your bottleneck. The rest of the specs sound great for this game.

You shouldn't force an Intel with too much effects, especially with an OpenGL game. Don't know your particular model, but Intel cards I've known don't perform too well in OpenGL, no matter how much memory they have.