If it could be possible to "redo" a Windows administrator
password so easily when a password has not been set,
then is it possible to do so when one _has_ been set?

If so, it makes Linux look all the more appealing for
people who need security, as if there weren't already
enough reasons.

On that note, other, larger questions that are probably
answered somewhere in the documentation:

If I install Ubuntu, there is no root password;
The privilege is automatically given me to
"admister the system" (in the program "users-admin"
which can be launched from the System Menu).
That privilege makes me a "superuser," correct?
Is that what superuser means? Else, what?

I have the option of creating other users with
admin privileges. I note that those users, at
default, anway, are capable of changing my
password. I don't feel comfortable with that.
Is there a way to deny other users who have
permission to "administer the system" from
being able to change my password? I did set up
a Linux guru with admin privileges and arranged
for him to access my computer remotely if it
ever becomes necessary. I trust him not to mess
me up; if I didn't then I could reset his password
right now and reset it back to his original on
any needed ad hoc basis. Still, I'd like to know
if there is a way to protect myself absolutely
from other administrators.

If root privileges are necessary then in Ubuntu we
use sudo [command] or sudo -i. This is a security
design feature to make it harder to hack in from
outside ("root" plus a password is easier to
hack into than some unknown user name plus a
password). In other Linux systems where root is
used for administrative tasks does this situation,
which I deem a weakness, exist?

Finally: regarding my first question about whether
an already set Windows XP password can be reset via
the Administrator account in safe mode, even if it
cannot Frank cited

www.psychocats.net/ubuntucat/how-to-reset-a-win\
dows-xp-password-with-ubuntu/

so I understand, at the minimum, it's possible to redo
an unset admin XP password from outside Windows.
(Win XP oughtn't allow an unset password anyway; it
wouldn't happen in Ubuntu.)

Is there likewise a way to redo a forgotten Ubuntu
only-one-administrator password, without reinstalling
the OS? If so then it would be as weak as Windows XP
in this regard.

And, as (I promise) the truly final corollary, is there
a way to prevent such a malicious action that involved
reinstalling Ubuntu from preserving the existing home
directories which might contain sensitive data?