Join network clients to new domain

I need to join a couple of computers which were formerly in another domain (now non-existent)  to a new SBS 2012 Essentials domain.  These other computers are currently functioning as standalone computers and can access some files on the computers in the new SBSE 2012 domain as if they were part of a workgroup, but this is clunky.  How is the best way to unjoin these computers from the old, defunct domain and connect them to the new SBSE 2012 domain, keeping as much of the configuration of the computers as possible (i.e., we do not want to have to reinstall programs like Adobe and Office, if possible).