NT login passwords are hashed with a message digest algorithm, which
is irreversible. The only way to recover a login password is by
repeated guessing, i.e., a dictionary attack or a brute-force attack.
Nope.
Define what you mean though, all "NT passwords" are not the
same protection level.
Ever heard of L0phtCrack? It'll do NT4 and sometimes NT5
(if NTLM hash use is retained for backwards compatibility).
Even if we ignore this, what you call "guessing" at it, is
in fact cracking it, particularly when done in an automated
fashion. If you don't like the word "cracking" for this
use, that's a bit beside the fact that the entire industry
has settled on it- so find another word you like better and
then convince the entire industry to switch to using that
word instead of "cracking", else "cracking" is the proper
term.
Then your distinction between "guessing" and "cracking" is
pointless. ANYTHING that is yet to be solved, initiates
with guesses about the strategy to use, later confirmed by
evidence. With this case, it's just a short leap from the
former to the latter when the password is accepted.
There are plenty of Google hits for UFO abductions, too, but that
doesn't mean that they occur.
Nor does it mean they don't occur, but in this case, people
have in fact cracked passwords, there is no denying it.