If you are using SQL Server 2005, you must also change the surface area settingsConfigure surface area settings in SQL Server 2005
1. Click Start, point to All Programs, point to Microsoft SQL Server 2005, point to Configuration Tools, and then click SQL Server Surface Area Configuration.
2. In the SQL Server 2005 Surface Area Configuration dialog box, click Surface Area Configuration for Services and Connections.
3. In the tree view, expand the node for your instance of SQL Server, expand the Database Engine node, and then click Remote Connections.
4. Select Local and Remote Connections, select Using both TCP/IP and named pipes, and then click OK.