Microsoft will end extended support for SQL Server 2005 on April 12, 2016.  No further security updates will be made.   Microsoft recommends that SQL 2005 users upgrade to a paid SQL Server 2014 license.

More information is available at http://blogs.microsoft.com/blog/2015/04/13/are-you-still-running-sql-server-2005-now-is-the-time-to-upgrade-to-a-modern-data-platform/

and

http://www.microsoft.com/en-us/server-cloud/products/sql-server-2005/? wt.mc_id=WW_CE_MU_OO_BLOG_NONE

SQL Server Express 2014 is free but limited use database, available at https://msdn.microsoft.com/en-us/sqlserver2014express.aspx.