2 days ago I did the routine system back up and, in the process, I was also trying to retrieve missing images from 1 folder. The missing images are not important however, this morning I discovered that EVERY folder in my Library has disappeared. Some images were on my C drive and many were on my F drive. The only folder remaining is the folder that had the missing images. Please advice what I can do to fix this? I've been using LR for about 1.5 years now and have never had this problem before. Thanks!