How to solve Named Pipes error 40 when connecting to local MS SQL Server instances

I was getting the following error when trying to add my local MS SQL server 2008 Express database to the data connections in Visual Web Developer 2008 Express :

Named Pipes Provider, error: 40 - Could not open a connection to SQL Server

The problem was that I was using just (local) in the server name field. To solve the problem, I had to add the instance name (sqlexpress) like this:

(local)\sqlexpress

When I entered that into the server name field, everything worked perfectly.