1) Disable any MSI applications (eg. performance / monitoring apps).
2) Ensure your graphics drivers are up-to-date from the manufacturer, not the Windows Update.
3) Check that your display resolution settings are not above 100% zoom.
4) As a last resort, you can try disabling the OpenGL setting in the rekordbox3.settings file. Find <VALUE name="DisableOpenGL" val="0"/> line and change to "1". That file is located in this folder:
C:\Users\yourusername\AppData\Roaming\Pioneer\rekordbox
