I just performed my last Windows NT to Windows 2000 domain migration (I certainly hope it's the last time!) I was tasked with moving an NT 4 domain with a single domain controller to Active Directory. Fortunately, the company did not have Exchange (I've done NT 4 + Exchange 6.5 to Win2k3 + Exchange 2003, and it's not a fun migration.)
Here are the steps I followed, more or less:
1. Obtained Windows NT Server media, Windows 2000 server media, and Windows 2003 R2 32bit media
2. I migrated the existing NT 4 server to a VMware server 1 VM (the company only had a single VMware server running on CentOS 5.2. I used VMware converter version 3.x (version 4 does not support NT 4.)
2a. I had some time on my hands, so I simulated the whole thing with a copy of the VM I created in step 3. I did the entire migration on virtual machines before continuing on site.
2b. I created a snapshot of the virtual NT 4 PDC.
2c. I set up an additional DNS server on another box (a windows 2003 server) and made it the primary DNS server. It is possible to use Bind 9, but the client did not have enough unix infrastructure to make that practical.
3. I created a Win NT BDC as a VM on Sun VirtualBox 3.x. I created a single disk of less than 4GB (I made it 3.8GB.) The disk did not need to be huge. I was not intending for this VM to be around long term. This worked fairly well. I originally tried to create it using VMware Workstation 7.x, but had several annoying problems, so I just used VirtualBox. The NIC on the VM was bridged. I gave it a static IP and put it in DNS.
4. I promoted the VM I created in step 3 to be the PDC (using the server manager on the original NT 4 PDC.
5. I created a snapshot of the new NT 4 PDC
6. I upgraded the new PDC to Windows 2000. I ran into some problems with the VM crashing (VirtualBox crashing, to be precise.) I stopped the crashing by disabling all virtualization extensions on the VirtualBox config for the VM. At any rate, this created an Active directory installation. I pointed DNS to the win2003 server I mentioned in step 2c.
8. After the upgrade and Active directory creation, I made the new win2000 box the primary dns server for the zone. Once I had transferred the zone successfully, I changed the zone to be active directory integrated.
9. I applied Windows 2000 Service pack 4 and all relevant updates ( I had to install IE 6 sp1 to get windows update to work correctly.)
10. I ran adprep /forestprep on the new windows 2000 domain controller. Adprep was located on the second disc of Windows 2003 R2 32bit in the directory CMPNENTS\R2\ADPREP.
11. I ran adprep /domainprep and adprep /domainprep gpprep on the Windows 2000 domain
At this point, I had a Windows 2000 domain. I could safely delete the NT 4 BDC and shut it down. I left it around, as there were a few files to grab.
12. I then ran dcpromo on the Windows 2003 box I mentioned earlier, and made it an additional DC.
13. I made the windows 2003 R2 dc a global catalog server.
I haven't had time to go back and finish up (add another Windows 2003 R2 box (or even Windows 2008 R2)) yet. I verified that filesharing and login worked, of course.