"After the installation of Small Business Server is completed, the domain name and computer name should never be changed. Changing either of these settings may cause problems that will require a complete reinstallation of Small Business Server.
Changing either the domain name or computer name is NOT SUPPORTED on Microsoft BackOffice Small Business Server.
Each application is configured with the settings chosen during the initial installation and would all need to be changed individually.
This scenario is also explained on page 131 in Appendix A of the Start Here Guide that ships with Small Business Server.