If you are unable to do a direct upgrade of your NT or Windows 2000 domain, you can create a new Windows Server 2003 domain and migrate users, computers, and groups into it from an existing domain. Microsoft provides several migration tools in the shrink-wrap for this purpose. The most rudimentary of these tools are a set of scripts for cloning security principals between domains. They are as follows:
Clonepr. Copies a user account to the target domain.
Clonegg. Copies Global groups to the target domain.
Clonelg. Copies local groups to the target domain.
Cloneggu. Copies Global groups and users to the target domain.
Sidhist. Takes the SID of a user or group from one domain ...