OK, progress--got LR to see all my photos, but none of the collections came through. It looks like the photos in which I edited in PS came through with all the edits, but any rankings or collections did not. How can I find the missing collections?
I did it!!! I did it all by myself, with a little help from Julianne Kost! Thank you, Julianne. You are truly a wonder woman. No thanks to the 57 people who read this forum post. But if one person reads this one and it saves them some time, then this time will have been worth it.
My main computer crashed and Windows had to be reinstalled to like new factory condition meaning that allll software needed to be reinstalled. Good news is that I had saved the important folders off my old C drive and had a doc with all my product keys in it. I got LR re-installed, but first it couldn't see any of the photos. Yesterday, I got that task done using a Import from Catalog command, but I must have chosen the wrong catalog. Today, I watched Julianne's tutorial on Lightroom backups and found that indeed there is a path where LR does tell you where the magic catalog is stored and I had it in my old folder. I looked under C/Windows.old/Users/Carol/MyPictures/Lightroom and there is was--a file called Lightroom Catalog.lrcat. Went to Import from Another Catalog and chose that one and waited a very long time. Eventually, all my collections showed up, all the flags, rankings, sorts, presets, etc are there. It's magical.
Now that you have seen the need for backups, you need to make sure of two things:
1. Make sure that LR is creating backups of your catalog on a regular basis.
2. Make sure these catalog backups are on a different drive from your active catalog. By a bad default, LR 5 and 6 put the backups in a subdirectory of the active catalog. (Not sure where LR4 puts them.)