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) (Microsoft SQL Server, Error: 2)
1) Name of instance (No offence, it usually gets me, too). Check the name of the instance in the services applet. Instances will be listed as SQL Server (instancename)
2) Is the SQL Server service for that instance running?
3) Is the SQL Browser service running? SQL Browser acts like a switch to direct your request to the correct port number for the instance you have called for.
4) Has someone activated the firewall on the server?