I’m positing this with the hope that helps someone else avoid frustration.  For several months I had overscan issues displaying HDMI from my computer on my Panasonic Vierrra TH-42PZ85U.  The TV always cut off the borders of the screen.  I searched forever for overscan options for the TV, and even tried to write custom modelines without any success.  Many posts in forums were reporting similar frustration.  However I finally found a simple solution.  On the TV, go to  Menu->Picture->Advanced Picture->HD Size.  Changing HD Size to 2 fixed the problem!