For those who care to learn from my mistake.
My home computer has two physical hard drives. The C drive for the OS and programs and a D drive for data storage.
I copy from my camera to a folder I set up on the Desktop C drive. That way I see it everyday and after I get a few it is a nagging reminder to catalog and file these images. As I said in this case a had about 6 weeks of photos to go through. I organized them and copied them to the D Drive. As soon as I did all that work I did a full overnight backup. I did not realize it at the time but the files did not copy properly to the D drive. So I got a backup of corrupt files. OOPS!
If I had gone and checked the files manually I would have seen they did not copy properly. So over the next 2 months I made several more backups of garbage. When I did go to get the photos when someone requested them they were not readable. I did have six perfect copies of corrupt files.
Other aspects of my “perfect” system were.
Two external hard drives. I do a full backup once a week and do another backup of new of changed files mid week. On Mondays I unhook the drive connected to my home computer and take it to work and bring the other dive home with me to start the process again. That way I always have an off site backup in case my house burns down. Each drive is large enough to copy my computer three times hence my six copies.
As MartinP pointed out I need to be more careful. Any by the way the issue was that my D hard drive was failing and I have replaced it. This was the first symptom of the impending total failure that it had.
I also do all of my own B&W developing and have scanned untold thousands of negatives and slides. I do not want to even think of how may hours of work I would lose if I had no backup.
Now that I am worried about a tornado where do I store my negatives? Perhaps I need a bomb shelter :-)