You may receive the following error when launching Microsoft Discovery and Risk Assessment Server 2013:
An unexpected error has occurred: Could not load file or assembly 'System.Data.SqlServerCE, Version 18.104.22.168, Culture=neutral, PublicKeyToken=89845dcd8080cc91' or one of its dependencies. The system cannot find the file specified.
The reason for the error is that Microsoft SQL Server Compact 4.0 is not installed on the server. This is required for Discovery and Risk Assessment Server as documented here:
Download and install Microsoft SQL Server Compact 4.0 from here to fix the error: