How can I make the X-Arcade™ Trackball more or less sensitive on my PC?

Go to the "Mouse" section of your Control Panel in Windows™, under the "Pointer Options" tab adjust the "Select Pointer Speed" bar to faster for more sensitive movement, less for slower movement.

This menu may be slightly different if you have 3rd party mouse software installed. Remember that this adjustment will also effect any other mouse you may have connected.