How can I join a computer to a new domain remotely?

Sure thing. The NETDOM utility is "your friend" in this case. I've deployed a startup script in the "old domain" to cause computers to disjoin their existing domain and join a new domain.

Some docs on NETDOM are here:

• http://technet.microsoft.com/en-us/library/cc737599(WS.10).aspx

You'll need to create a user in the source domain and destination domain with rights to add/remove computers from the domains for NETDOM to use.

NETDOM move %COMPUTERNAME% /d:NEWDOMAIN /ou:DN_of_destination_OU_in_new_domain /ud:admin_user_in_new_domain /pd:admin_pw_in_new_domain /uf:admin_user_in_old_domain /pf:admin_pw_in_old_domain /reboot

So, let's say that the new domain is "newdomain.com", the computer needs to go into the "OU=Desktop,OU=Client Computers,DC=newdomain,DC=com" OU, the user w/ rights to remove comptuers from the old domain is "oldadmin" (with the password P@ssw0rd), and the user with rights to add the computer to the new domain is "newadmin" (with the password dr0wss@P).

NETDOM move /d:newdomain.com /ou:OU=Desktop,OU=Client Computers,DC=newdomain,DC=com /ud:newadmin /pd:dr0wss@P /uf:oldadmin /pf:P@ssw0rd /reboot

BTW: If you want to forcibly disjoin the computer from its current domain w/o actually contacting a domain controller there, drop me an email. I have a utility that I've written (but don't have it handy right now) to tell the computer it's no longer a member of a domain w/o contacting the DCs in that domain. It's quick-and-dirty, but it works if you need to get a machine out of a domain and have local Administrator access but no domain rights... heh heh...