There have been some changes to Microsoft Agent for Windows Vista, as explained at http://msdn2.microsoft.com/en-us/library/ms695905.aspx.

If you are running Windows Vista and you do not hear narration from the Agent control when using any of the "Learning & Mastering ToolBook" CD's, you likely need to install the 4.0 version of the Microsoft Agent SAPI speech engine. You can download and install SAPI 4.0 using this link: (http://activex.microsoft.com/activex/controls/sapi/spchapi.exe ).