To get to the emergency restart option, you need to press the familiar Ctrl+Alt+Del keyboard shortcut, known by pretty much everyone who's ever had to fix a Windows PC at some point. This shortcut is designed to work even if your computer is otherwise unresponsive, and gives you access to options for locking your PC, signing out of your account, and bringing up the Task Manager.

Down in the lower right corner, there's also a power button: Click this and you get the standard Sleep, Shut down, and Restart options. However, if you hold down Ctrl and then click the power button, that takes you to the emergency restart page, together with the warning about losing any unsaved data. Click OK, and your computer will reboot itself almost instantly.

If you can get to the screen after Ctrl+Alt+Del, then you'll want to try the normal restart option first—you'll only need to go down the holding Ctrl route if that doesn't work. Presumably, that will be because there's a program or a part of the Windows code that isn't shutting down properly to clear the way for a restart.