I had a 2TB HD that came with my computer but it was a bit slow. I bought a 600GB HD that is quite a bit faster and used AOMEI to make a total clone of the old HD on the new one. I only had 400GB used on the old one so it fit in just fine. I even have all the extra partitions copied to make sure it would boot perfectly. The new HD is an exact clone. But now when I try to boot off it I get an error message no boot file.