I have a Windows 2008 R2 domain, and I need to join a Windows Server 2003 machine to the domain. I have also lost any local user passwords to the 2003 machine.
Can I use Offline Domain Join to add the 2003 machine to the 2008 domain?
No. You messed it up.
This is not a problem of domain join.
You lost all passwords to the computer. How you expect to log in to join the domain?
If I could join a computer to a domain WITHOUT HAVING ADMINISTRATIVE ACCESS TO THE COMPUTER, this would be a hugh grave security issue (because I could give myself administrator priviledges through that).
Besides it does not work with a 2003 anyway. Use a password cracker.