Display Properties is in the Control Panel, or right-click the Desktop and select "Display" or "Properties". The exact wording differs between Windows versions, but it's the place where you do everything related to the monitor display.
The font smoothing settings are something else to look at, if resetting the Theme doesn't help. By "reset" I mean: select a different Theme, hit Apply, then select the original Theme and hit Apply again. This reloads all the original settings.