Which question exactly was not answered?

Where are login audits stored?

SQL Error log, if you configure auditing successful/failed logins through the instance properties. This is the same for every version of SQL.

MS documentation stating such:

SQL 2012

http://technet.microsoft.com/en-us/library/ms175850.aspx

SQL 2008 R2

http://technet.microsoft.com/en-us/library/ms175850(v=sql.105).aspx

SQL 2008

http://technet.microsoft.com/en-us/library/ms175850(v=sql.100).aspx

SQL 2005

http://technet.microsoft.com/en-us/library/ms175850(v=sql.90).aspx