Thanks so much for your responses. You've been most helpful.
I have not tried to reinstall yet. I've been waiting just in case other replies come in.
Someone else on another forum advised to run Terminal in Disk Utility and type in "diskutil list" and provide a screen shot. Based on the...
Actually I am not sure if I enabled File Vault but when I turn on the iMac, (before I was locked out of it, obviously) it would show the apple, then it goes to the login screen..I type login password and it goes to desktop. I don't recall seeing any "unlock" screen.
So I did what you said...
I have an iMac a couple of years old. Can't give any specs because I am locked out of it. I believe it is either el Capitan, not upgraded to Sierra.
I tried to login recently using a valid password. I couldn't get in. After several tries, I got in but a Keychain Access message saying "System...