How can I lag fix assassins creed 3 on my pc I have Intel(R) Pentium(R) CPU P6100 @ 2.00GHz?

If I correctly read your question you want to fix lag on assassins creed. Go into game settings and change your resolution to the lowest setting. Thats really the only way you can decrease lag, unless you buy a computer with at least 3GB of RAM and a dual core processor.