This solution describes an issue when Spotlight on Messaging is unable to connect to SQL Server 2005 Express.
By default, remote connections are disabled for SQL 2005 Express.
The following needs to be enabled in order to install Diagnostic Services on a different computer other than the Spotlight on Exchange Enterprise Edition database.
To enable remote connections
1. Open SQL Server Configuration Manager.
2. Expand the Protocols for <InstanceName> node, where <InstanceName> corresponds to the SQL 2005 instance to which you want to install.
3. Right-click TCP/IP in the right view and select Enable.
4. Restart the SQL Server services.
5. Then open Services and Start the SQL Browser Service and set it to Automatic.