it is the crazy way that manufacturers use different methods of describing their equipment. Looseley based on a GB being either 1000 bits or 1024 bits of info. They claim the best poss way of describing but in reality what you have is spot on. I use Acronis and when I set up a new pc and have it running as I like it I do a full image backup. From then on for at least a year I do an incremental backup ie only adding what has changed since the last one. On my present pc I had 3 hard drives fail. The original after almost a year which was replaced under warranty. The next 2 replacements failed after a couple of weeks. The 3 rd. replacement is still ok after 4 months. Each replacement has been set up using only Acronis. No format just running the cd I made up from the original acronis setup.