I had initiated what became a long series of messages re failure of
nmap, and failure of other basic system commands on a
refurb Dell Optiplex 780 computer obtained from Discount Electronics.

It turns out that this computer--maybe all Dells of that 8-year-old
vintage--contains a setup system which defines the way
that the computer can be used, regarding bootup source, and various
things, some of which are not visible, having been
deliberately hidden by that very same setup function.

This was probably a reasonable approach for the commercial office use it
was refurbed from. It is designed to keep a user
from messing with the way the computer performed. A lot of features
which are visible during boot are not reachable
by any means, at least by me, and apparently by a man named Joe at
Discount Electronics.  The computer even has a
means of applying a padlock so that it cannot be opened up by a user!

During an interchange with Joe, I told him that unless he can tell me
how to remove the nanny functions, I would
return the computer for refund. He told me that the company does not
take back units for refund, only for the sale
of a newer computer.

This was to be only an interim machine, since all my computers were
damaged by lightning. Now I will return it to Windows
and donate it. I am fortunately financially able to do that. But I am
writing to warn anyone contemplating a purchase from
Discount Electronics, DON'T!

If you intend to run Linux--as I'm sure all readers here do--then don't
purchase from Discount Electronics. And make sure you
get a written promise that you will be allowed to return for refund if
the machine you purchase (somewhere else!) is not
suitable.

(For myself, I have come up with an HP laptop on which I will try and
run Linux--HP says no problem, but I haven't tried
it yet. I have to say that for a machine that originally ran Windows 7,
it is impressive with Win 10 on it.)

--doug