Excel Services is installed as part of SharePoint Server 2007 but is not enabled by default. To make use of Excel Services, a few additional steps are required to configure it in an SharePoint Server 2007 installation.
To configure Excel Services, you must first install an instance of SharePoint Server 2007 in either the Complete or Web Server mode. Once it is installed, you need to create a Shared Services Provider (SSP). Excel Services is a shared service that is available only from an SSP. There are two parts to configuring Excel Services. First you need to enable Excel Services and then you need to configure a trusted connection.
For details on configuring an SSP, see Chapter 18.