sql server give this problem ?

Question

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)

NOTE:- i am 2 times installed sqlserver .. but same problem is comeing .

pls tell the solution