I recently got hold of a second hand but almost unused Sony Trinitron Multiscan 200ES monitor. The display is excellent but I notice a really big difference if I uncheck the "Hide modes that this monitor cannot display" and select 120Mhz rather than the 85 that is the max with option checked. Am I really risking damage to my monitor by doing this, or does the fact that it works suggest It'll be ok? Has anyone heard of a monitor being truly cattled by running it at too high a rate?
it would have been the case that your monitor would have been damaged if you tried to run it at too high a refresh rate.
A modern monitor will almost certainly have a protection circuit that puts it into energy saving mode if either of the sync signals are out of the monitor's recommended range. You won't really notice any difference between 85Hz and 120Hz (note that it's Hz not Mhz by the way)but your eyes will, so run the monitor at the higher rate, provided you experience no degradation in image quality.