BUILTIN\Administrator
By default, the local Windows Group BUILTIN\Administrator is no longer included in the SQL Server sysadmin fixed server role on new SQL Server 2008 installations.
If your processes or code depend on Windows BUILTIN\Administrator local group access, you must explicitly grant permission to log on to SQL Server. Accounts are no longer automatically granted access to SQL Server because of their membership in the Windows Administrator group.
Refer to: http://msdn.microsoft.com/en-us/library/cc280562(v=sql.105).aspx
