A decent (though not terribly crafty) analogy is that
the computer is
now like a pad of paper and a pen. You come in and use the paper
that you need, then rip those pages out and take them with you. The
pad is then made fresh for use for the next person.
This would be good, if it were the way it worked.
Places that do that (start clean for each new user) are notable by
their rarity - and how many of them do you think went to the trouble of
making sure their motherboards either didn't have flashable BIOS or had
a hardware disable on it so that you can't reflash them without opening
the case? I'd guess it didn't even cocur to most of them.
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