Touchpad

I have a Latitude D820.  I know very little about this machine..  But know all of a sudden I am having trouble wiht my touch pad.  Sometimes the ursor just goes haywire all over the page and sometimes wont move at all.  It will land on something and just open things up as it goes past..  just some really odd behaviors.  I have tried the preferences to reset them .. nothing changed.  I dont know what else to do for trouble shooting this problem.  HELP any suggestions would be greatly appreciated!