According to Microsoft"s bulletin on the matter "in Windows 2000 a hierarchy of container objects is used to separate processes. Every session contains one or more windows stations; every windows station contains one or more desktops. By design, processes are constrained to run within a windows station, and the threads in the process run in one or more desktops. A process in one windows station should not be able to access desktops belonging to another windows station. However, due to an implementation error, this could happen under very specific circumstances."