We are long past, but beginning with SQL Server 2012, security privileges changed and you cannot use the LocalSystem account as you could previously for authentication. You used to be able to use the LocalSystem account as the default for the sysadmin role, however you now must use one of the following authentication methods. For authentication with SQL Server 2012 or later you must use a domain account (including Administrator) that has the SQL Server sysadmin role OR change the Log on as option for SQL Server Service to use a domain user that has the required privileges.
If the SQL Server is not part of a domain, you can use a Local user that has the sysadmin role or change the 'Log on as' option for SQL Server Service to use a local user that has the required privileges.
CREATE LOGIN [<domainName>\<loginName>] FROM WINDOWS;
*Click the link for more information: CREATE LOGIN (Transact-SQL)
*Click the link for more information: SP_ADDSRVROLEMEMBER (Transact-SQL)