We are trying to migrate from a member server to a member server. The target server has been demoted from a domain control to a member server. When we start the migration the only option available is to migrate from a member server to a domain controller.
This issue is caused from a failed demotion. ServerMigrator, still recognizes the server as a domain controller or a workstation.
If the demotion failed to remove AD from a Windows 2000 or 2003 domain controller (DC) when it was converted from a DC to a member server,
Change the ProductType's data value to ServerNT. (Use the exact case.)
Shut down and restart the server.
Delete the NTDS folder if it exists.
Also, The following Knowledge Base articles may be helpful.
HOW TO: Remove Data in Active Directory After an Unsuccessful Domain Controller Demotion (Q216498)
Domain Controller Server Object Not Removed After Demotion (Q216364)
Once the demotion is completed ServerMigrator will recognize the server as a member server.