marcuswon,
You do not need to use HumminbirdPC to update the software in your units. It is only used for those units that do not have an SD card slot. Just download the software directly to the SD card. In fact the latest software for the 798ci unit is not on the web site. I would add it but it seems I am having problems uploading software this morning so you should go to the Humminbird web site and register you unit and download it from there.