Thanks, Tony. I hadn't thought to try it with the battery (didn't make a difference, but it was a Good idea!) When I tried opening with Safe Mode, it gave me a screen full of number stuff that I didn't understand at all. The error message (non-system disk or disk error) shows when I try Start Normally.
I don't remember what screen I got when I hit the one about Starting at Last Workable Settings (or whatever it says..something like that)

I tried 999's idea of just searching with the error phrase and now I'm following directions that I don't understand but seem easy to follow. Maybe that will work.

Thanks!