How to increase cpu fan speed, I have asus p5n73-am motherboard and dual core 2.5 ghz 2gb ram?

The problem is, there is cpu pressure when opening normal flash or normal movie play or heavy graphics in website cpu temp rises beyond 55c or 60c sometimes 70c also. consequently cpu fan speed does not rise very much, Its just 2050 to 2110 rpm. Further fan speed increase can easily cool it to 45- 40 or less.i have cleaned cpu fan dust also what settings can be done in bois to increase speed, or any other remedy. awaiting best answer.