I could not change the refresh rate of monitor as no rate is there

Hi, To have maximum performance of the monitor, i tried to change the refresh rate of monitor from 60 to 75 hertz. But on going to the advance menu and monitor, there is no hertz to select, it is set to use hardware default settings. thereis no drop down menu showing the hertz. How to have thoses hertz.
I remember seeing those hertz sometimes back. My OS is window 7 ultimate

Could i expect the reply. Why refresh rate is absent