Thank you for all the help.
My 1TB USB HDD has FAT32 and >1000 videos.
It was connected to a TV set. All files suddenly disappeared.
When I connected it to Windows, it said it needed repair.
>1000 videos became .chk files in a hidden folder. I moved them to a new folder.
My problem is all file names are missing, as TestDisk list shows.
It's too hard and time consuming to rename them.
TestDisk finds only one partition.
I tried Undelete. It just lists the .chk files.
Partition Write saids "Write error".
PhotoRec only found 20 mp4 files without original names.
Rebuild BS has a side effect of listing all files in the log file.
Interestingly, the log file now shows the .chk files plus >200 original file names!
But in app, the list was empty, and the log says "Can't list files, bad root cluster."

If I could recover those >200 files with their original names, it would help save much time.
Regards.