I have just done a domain upgrade myself on a 40-50 user
environment. Safest way to do it is as follows.
Get a reliable machine (does not have to be a server) and
install it as an NT bdc. Make sure it is synchronised with
the pdc then take it offline incase the upgrade fails.
Next get a new server and install it as an NT4 BDC.
Promote it to the pdc and upgrade this machine to 2000 -
it will automatically make it a DC. Asap get another
version of 2000 server (either upgrade a bdc or another
new machine) and make it a DC for fault tolerance
You now have a 2000 domain and can either remove the NT
bdc's or upgrade them.
If it all goes wrong when you upgrade simply remove the
2000 machine, plug the bdc you took offline in and make it
the pdc and your network will be the same as before you
did the upgrade.
Hope this helps
