Actually, I did not move between systems. I had not done anything. One day the SONOS speaker system could not play the music (all CD's). The CD's were loaded via iTunes over the years, but I had not loaded any CD's recently. In researching the SONOS issue, I found out that I could not open iTunes. About a week before that, I remember the DELL computer did an update. There may have been a Windows update too.
I now have iTunes set up to NOT do automatic updates. I'll see how this goes.
I got to thinking that if this happens again (and iTunes has had problems in Windows before, as I can tell from my notes over the years) I will try to download iTunes from my backup. This is a good reason to do backups!