JSI Tip 4480. How do I use a Windows .NET Server to create a configuration in which two users can control the same session on a Windows XP Professional-based computer?

Microsoft Knowledge Base Article 279656 contains the following summary:

Users can connect remotely to a Terminal Services session that is running on a Windows XP Professional-based server. However, in Windows XP Professional you cannot create a shadow session, where a local user and a remote user can control the same session. This article describes how to use Windows Server 2003 to create a configuration in which two users can control the same session on a Windows XP Professional-based computer.