LeoMoon SessionGuard is a free portable app capable of preventing your machine from sleeping or restarting without changing any settings.
It works by registering a ShutdownBlockReasonCreate() reason and objecting to WM_QUERYENDSESSION messages. It resides in the systray awaiting deployment and includes limited settings like emulating mouse move, start with Windows, and hotkey selection.
An app such as LeoMoon SessionGuard is useful when your employer forces screen-saver/screen-timeout to lock your computer as part of their internal policies, for instance. Or just for personal use when watching movies or other activities that require a stop to the screen-saver activating. LeoMoon SessionGuard is also capable of stopping Windows automatic restarts.
LeoMoon SessionGuard Features:
Does not modify any Windows settings
Stops screen-saver/screen-timeout to lock your computer using SetThreadExecutionState
Stops system restart using ShutdownBlockReasonCreate