An overly technical report of shutting down windows can be found
here.
Worth noting is the interrelation between "HungAppTimeout", "AutoEndTasks", and "WaitToKillAppTimeout":
If the messages aren't processed within the timeout period (registry key HKCU\Control Panel\Desktop\HungAppTimeout), CSRSS will put up a dialog box asking if the process should be terminated. Using the registry key HKCU\Control Panel\Desktop\AutoEndTask you can specify that the dialog box shouldn't be shown and CSRSS should just terminate the thread. If the the WM_ENDSESSION message is processed but the thread doesn't terminate within the timeout specified by HKCU\Control Panel\Desktop\WaitToKillAppTimeout, CSRSS will terminate the thread. When all the top-level windows have been destroyed CSRSS will terminate the process.
