As I have written, Windows Defender is not listed as installed.
If I try to reinstall it, I get an error message that says
Windows Defender is part of Vista and there is no need to install it.
I would be happy if any of the following things were possible:
(1) install Windows Defender and have it work
(2) remove Windows Defender and have my system stop
complain about programs being blocked at start-up
(as I wrote: when my system is started an icon on the lower-right corner complains about some programs having been blocked but if I try to select
"Mostra o rimuovi [show or remove...]"
I get an error with "...0x800106ba...".