Please help with not booting from USB so to install Debian

[Rodolfo Medina <rodolfo.medina@gmail.com>]

I want to install Debian on a new machine but don't manage to boot from USB
stick.  (I can do so regularly with another machine, so the USB stick is ok and
so is the Debian netinst I burned onto it.)  At the boot I press F9 and a menu
appears where I can choose to boot from USB stick; but then it doesn't so at all
booting instead into Windows 11.  In BIOS I enabled the CSM protocol but
nothing.  Please help as I don't know what to do: thanks.

Rodolfo