shutdownBlocker is simple program that intercepts & blocks shutdown / restart / logoff commands. It protects from user mistakes, poorly designed installers (those lacking a 'restart later' option), and even windows itself (looking at you, 10).

It works by registering a ShutdownBlockReasonCreate() reason and objecting to WM_QUERYENDSESSION messages. It can optionally be set to consume all calls to shutdown.exe and MusNotification.exe (among other things, this blocks Windows 10 Update restarts); but this requires running the app as an administrator.