at 60hz you will see flicker.
85hz and above will stop this happening.
your monitor may not support a higher refresh rate if its an older model.try setting the resolution to 800x600
go to control panel/display/settings/advanced/monitor and put a tick in the box that says "hide modes this monitor cannot display"
then choose the highest refresh rate from the drop down box.apply and ok.
some games will,even if you have set as above,revert back to 60hz.
if so then try click here