Massive Stutering in assasins creed 2 for the PC

Hi there
I recently bought assasins creed 2 for the PC via Steam and when i tried to play it i noticed some realy heavy stuterring going on , the framerate seems solid but the game stutters very frequently...
I wonder if any of you have experienced the same problem or if there´s a fix to it
PS: Im runing the latest patch , the latest GPU drivers and my HDD is defragged
Specs:
AMD 965 BE 3.4 GHZ quad core
Gskill Ripjaws @ CL 7-6-7-24 1333 MHZ 1.60V
Asus M4A79XTD EVO
Samsung Spinpoint F3 500 GB HDD
Ati Radeon HD 5850 @ 1900x1080
Corsair TX 650W
Antec 300
Win 7 64 bits