Claudio,
In addition to what Chriss, Jack and Jerold have suggested I can come up
with two other methods:
1) ldifde
2) ADModify.
ADModify is a GUI tool that you can download and install on any WIN2000
Server ( does not have to be a DC as you have to 'connect to:' a DC. It is
a great tool for changing several fields in a bunch of users accounts at
once. There are, however, some limitations to it.
ldifde is another really great tool that is a bit more involved than
ADModify but does not 'suffer' from those limitations. You would have to
create a file ( with a .ldf file extension ) and then use the CLI to do it.
HTH,
Cary