The links below have sample scripts on how to encrypt data in SQL Server 2005:

http://blogs.msdn.com/b/lcris/archive/2005/06/09/simple-demo-for-how-to-encrypt-and-decrypt-a-table-column-in-sql-server-2005.aspx

http://blogs.msdn.com/b/lcris/archive/2005/06/10/sql-server-2005-column-encryption-demo-part-2.aspx

http://blogs.msdn.com/b/lcris/archive/2005/12/16/sql-server-2005-yet-another-column-encryption-demo-quot-clinic-quot.aspx