Need For Speed: Most Wanted 2012 HELP!!

[jus2ruff]

Hello Guys! I recently Purchased Need for speed Mostwanted 2012 from here. I installed it and it ran perfectly..but during gameplay it starts to stutter and goes below 4fps..while at some places its at 30+fps. My PC specs are below

P4 3.2GHz HT

1.5GB RAM

500GB HDD

Geforce 8600GT DDR3 256MB

My specs are pretty low but it also lags on my Lifebook LH-520 Which has awsome specs....Please Help me as i wanna play this game real BAD! =(

Haris