Migrate AD DS Server 2003 to Server 2008 R2

Solution 1:

Maybe I'm missing something, but why wouldn't you just add the 2008 R2 server as a server in the domain and then promote it as a second DC? Then transfer the FSMO roles and either keep the first server online for redundancy or demote it and remove it. THAT is the most effective way to migrate a 2003 DC to 2008 R2 as it preserves Group Policies, User Passwords, and all account and group information, not to mention security.

More details can be provided but I wanted to make sure there wasn't some reason you had already discounted this idea.

Solution 2:

I assume you are talking about migrating to a new domain. In which case, Active Directory Migration Tool is the most effective, thorough way to do this.

If you are talking about migrating to a newer domain controller in the same domain, then just prep the forest and domain with ADprep, promote the new server as a replica, transfer all FSMOs to it, and decommission the old. Then raise FFL/DFL if desired.