Are you using SQL Server 2005 Express? Don't miss the server name syntax Servername\SQLEXPRESS where you substitute Servername with the name of the computer where the SQL Server 2005 Express installation resides.
When to use SQL Native Client?
This connection string (Standard security using SQLNCLI OLEDB) can be used for connections to
SQL Server 2000, SQL Server 2005 and SQL Server 7.0.
Start over in the connection string reference index.
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