We did this on a test AD 2000 server we built. There's probably an easier way within 2000 but this worked for us.
Using your original NT server PDC, make an emergency repair disk using the /s switch. ie
rdisk /s.
This backs up enough registry information including the user account database (I think this is the sam database).
On your new server, install NT, giving it the same name as your original NT server. Once installed and working, power down the server, and start up again with the nt server startup disks. Use disk 1 then when prompted disk 2, I think it then gives option to do a repair. Opt for repair using erd you've just made. You then get option to restore the user database. Do this, then follow instructions to end repair. Reboot server and you should have NT server with all your accounts in place. Then do an inlpace upgrade to 2000, install AD and you should have all users there on AD.