ASP or ASP.NET site is running on IIS 7.5.
SQL Server 2008 R2 Express (10.50.1600.1) running on Windows 2008 Server R2 (W2K8 R2) x64.
You will see one of two errors depending on whether you dealing with ASP or ASP.NET sites.
On ASP.NET sites you will see “Server Error – Error: 26 – Error Locating Server/Instance Specified”
Server Error in '/YourApps' Application. 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: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)
On ASP sites you will see error 80004005, when trying to open an ASP web site
Microsoft OLE DB Provider for SQL Server error '80004005' [DBNETLIB][ConnectionOpen (Connect()).]Specified SQL server not found.
Run “SQL Server Configuration Manager” and enable TCP/IP protocol for you SQL instance:
To fix ASP.NET error message 26, you also need to enable Named Pipes protocol (picture above) and start SQL Server Browser service for a little bit.
Strangely, after your site begins to work normally, you can stop this service.
In both cases, you must restart you SQL Instance Service.
Problem solved. Hurray! Let’s go to solve some real problems