Now you can execute MSN desktop search queries directly from within your own applications. From there site:

Windows Desktop Search can also be queried programmatically so that the results can be displayed by another application. The ISearchDesktop interface is used to send regular queries to Windows Desktop Search and direct Windows Desktop Search DB queries (not recommended). IDL for the interface can be found in the downloaded. The methods and columns returned by Windows Desktop Search ISearchDesktop interface are in beta and may change in future releases.