A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)

Hi *.*,
This is one of the most frequently asking question on sql/asp fourms.
Reasons for this error:

1. Make sure your connection string data are correct and only that particular string is you calling.
2. You need to enable the listener on port 1433 in the SQL Server Configuration Manager control panel
3. Enable the "sa" user. It's disabled by default after the install.
4. Set a password on the "sa" user.
5. Enable SQL Authentication + NT Authentication mode.
6. Make sure the Windows firewall isn't blocking port 1433.
7. Try the default instance name instead of SQLEXPRESS.
8. Make sure the remote connection is using TCP/1433

If u had any trouble just ask, Happy to help u :) 
Stay Tune... 
Have a nice day... 'N happy Coding :)