Having tried 2 different Garmin etrex summit hc units to check if the problem was with the unit or connecting USB cable and also having tried all of the various suggestions from Garmin for downloading drivers and checking that Garmin could see my gps online (which they couldn't), I have returned the gps to Handtec ( who have ben remarkably helpful and prompt with the returns). I have managed to get my old laptop with a serial port back and will stick with my yellow etrex h. I know it's sad to let the technology win but life is just too short....