From The Desktop Heap Monitor is a tool that examines usage of desktop heap. The Win32 subsystem has an internal heap area known as the desktop heap. When you run a large number of Windows-based programs, an "Out Of Memory" error message may appear when you attempt to start new programs or try to use programs that are already running, even though you still have plenty of physical and pagefile memory available. This behavior can occur if the desktop heap in the WIN32 subsystem is depleted. By using the Desktop Heap Monitor, you can examine how much desktop heap is consumed without interrupting the running system. From : Due to its reliance on undocumented internal structures or maybe just because it's not an efficient use of time, Microsoft has so far decided not to release an update for the tool to allow it to work on operating systems more recent than Server 2003. So here's an update to let it do just that. Some improvements have been made over the original version. The tool now gives reports on all desktops present on the computer regardless of session, rather than just the current session. As it is not uncommon for desktops in different sessions to be similarly named, the session that the desktop belongs to is appended to the name.