If attempting to use the migration wizard in SBS 2008 or SBS 2011 from a domain with a standard windows server you will see the message
The migration wizard ONLY works from a SBS 2003, 2008 or 2011 server.
Migration guide from SBS 2003
Collated document for migration from SBS 2003
Something that may be useful to migrate a standard server to an sbs 2011:
Go to sbsmigration.com and order the migration kit for this project. In short terms you extract the AD information from your old domain and then migrate that information to a SBS 2011 server. Advantage from this method is that your SBS 2011 server can end up with the same servername and ip address as the original server.