Finally an upgrade that's gone rather smooth. We successfully upgraded an NT4 domain to a domain under an existing tree. We still have the original 2 DCs in case we have to rollback, but we'll redo them one at a time tomorrow. Snag 1 - NT4 BDCs are quirky. After isolating the original controllers the new BDC (whiterice - it's someone's nickname) didn't want to see the accounts and computers right. After deciding that if the accounts were really over we could copy the login scripts manually, we took the new BDC off of both networks and promoted it to PDC. This fixed the account problems, and allowed us to get working (we'll retrieve the scripts later). Then there's the having to "cancel" the upgrade to install SP2 so it doesn't keep crashing... Finally it was all done except replication, and we discovered the NTFRS database was corrupt (apparently not too uncommon). Now members of both original sides can sse and log into both domains, so the rest of this should go rather smoothly...