I'm not the most compter savvy person around so this probably isn't the best/most efficient way to do this, but it got the job done for me. Firstly, right-click on the desktop and click on Properties, then the settings tab, then the advanced button. Open up the graphics card tab and click on the 'change resolutions' menu and test to see how high you can set your refresh rate before your monitor cuts out, (Which was 85Hz for me). If you use a different resolution when ingame then change your normal windows resolution to that before testing it.
Next, download the
NVRefresh tool and open it up, (I know you said you did this, but it couldn't hurt to try again. It worked for me). Click on the 'Advanced mode' button and ignore the warning box that appears. Find the resolution that you use and change the refresh rate to match you monitor's max. Click Apply and restart your PC. You should be good to go. (Note: if you accidently set you refresh rate too high, start windows up in safe mode to set it to a lower number)
<- running Win XP home with geforce FX 5200 gfx card.
Hope that helps.