Well, I did a really stupid thing...
I deleted the Ubuntu partition, from a dual boot laptop. Now, whenever I start the computer, I see:
Minimal BASH-like line editing is supported.
For the first word, TAB lists possible command completions.
Anywhere else TAB lists possible device or file completions".
And I can't get out of here... from this bash.
The problem is that any of the suggestions on this forum assume that I have access to Windows, which I don't... but I am able to enter the bios.
I'm getting a bit desperate here...
I've tried exit in the bash, but I get sent to the same bash, after what seems to be a restart.