I am on my third computer/motherboard since summer. Each time I have reinstalled LR4, and then IMPORTED the CATALOG. This time for some reason, I am not able to see all my files. I am using Windows 8.1 and my photos are all on an external hard drive. I can see the pictures on the external, but not in my catalog. If I try to import them again, they will not, because it will not allow doubles.