1. Have DayZ 'Rendering Resolution' settings be set to something other than Windowed.
2. Start DayZ from Steam.
3. As you are within the initial 'Wait a Moment' or 'Receiving' loading screens, attempt to alt-tab from the game.
4. Observe as the game refuses to alt-tab, leading on to the 'Early Access Game' screen which then becomes unclickable, and inescapable.
5. Attempt to bring up the 'Ctrl+Alt+Del' sequence as the only means of escape, or turn off the computer manually.