not really your fault... the game is not well-coded.
still, you'd benefit more from a newer, gaming set up. ( e.g. core i5 2500k + 16 gb ram + cooler master hyper 212 plus + asus z68 motherboard + gtx 560/560ti + 80+ rated 550+ watt psu with good amperage on +12v rail)
have you tried overclocking your cpu? get a good cpu cooler if you do so.
the 2gb vram is wasted on the weaker gt 430 gpu. try to get one like 5770 (depends on your display res., budget, psu) to gtx 560 ti.