By default, the TCP/IP protocol is turned off when a SQL Server is installed to reduce security risk. But if you want applications to connect and access the SQL Server, you need to enable the TCP/IP protocol on the server by following this tutorial:

1. Go to Start > All Programs > Microsoft SQL Server 2005 > Configuration Tools > SQL Server Configuration Manager.

2. Double click on "SQL Server 2005 Network Configuration" to see the list of SQL Server instances.

3. Click on "Protocols for SQLEXPRESS". You will see a list of protocols.

4. Right-mouse click on TCP/IP and select the "Enable" command. See the picture below:

TCP/IP Protocol Enabled

5. Click on "SQL Server 2005 Services". You will see two services.

6. Right-mouse click on "SQL Server (SQLEXPRESS)" and select restart to finish the TCP/IP protocol setting change.

Your SQL Server is ready to accept network connection now.