Are you trying to use a refresh rate the monitor doesn't support?
You'll need to provide the exact model of monitor if you need further assistance.
no its set to hardware supported refresh rate, u cant change that.
and i dont know the model number its not my monitor but its a 22" 1600 x 1200 advent monitor
I assume "hardware supported refresh rate" only works properly if Windows knows what monitor you have.
Windows won't know what monitor you have unless you've installed drivers for it. Have you?
As far as the model number is concerned then they usually have a label on. Is it too much to ask that you look?