SQL Server Builtin Logins Migration
The following logins will be created on installation. They are containers for the accounts that the SQL Server Database Engine &amp; Agent run under.

 [NT SERVICE\MSSQLSERVER]

 [NT SERVICE\SQLSERVERAGENT]


The other accounts are groups that have been manually added into your SQL instance.

BUILTIN\Administrators was installed by default in SQL Server 2005 but not in SQL Server 2008 R2. 

I'd look at the permissions on the existing server to see what accounts are using these groups and then determine if they are needed.