- Press the Windows key then type in 'pow' and press enter (this should open the power options control panel)
- Click 'Change plan settings' on the power plan you currently have selected
- Click 'Change advanced power settings'
- Expand 'Power buttons and lid'
- Expand 'Start menu power button'
- Now change the setting 'sleep' to 'shut down'
- Click 'Apply' and 'OK'
Now the yellowish sleep button in the start menu has become a red shut down button.