Something went wonkers with my system, and although I could try to reboot

it would get so far and then fall back into some kind of maintenance mode.

Rather than fight it at the time, I thought it was a good time

to ensure I have a good backup of my home filesystem.

So I booted a Live USB stick and performed my backup.

Now I wanted to go back and try to diagnose/fix my root filesystem issue.

Sadly, my BIOS no longer knows about the bootable entity on the HD,

and only shows me the Flash drive (even if it's not plugged in).

Any idea what happened to my HD boot info in my BIOS, or how to restore it?

PS. It is a Dell laptop.

TIA

Fulko