1. Click on the Start Menu | Control Panel | Power Options | Change Plan Settings
2. Click on Change Advanced Power Settings.
3. Browse to “Power buttons and lid”. From there, you can change the “Start menu power button” setting to “Shut down”. Also, you can change it to “Hibernate”. You also have the option to change the default behavior for the case power button.
4. Click ok, and your start menu power button will now shut off your computer.