Migration Win2K server to Win2K3 server

I need Upgrade my Win2k server having DHCP DNS to Win2K3 server with Same domain name.

I installed win2k3 server as a PDC in different Server and configured AD.
Now i need to migrate all the users from win2k to win2k3.
1. I tride migration tool but it require two servers should be prasent in the network. but iam having same system name and domain name

I think u r done this job already. So please share u r experiance.