Just seen your reply re Win 10!
For Windows 10, if you click 'Windows Start'>'Power' it should display shutdown options, including 'Restart' .
If you press and continually keep holding / pressing down the shift key and then click the 'Restart' option, Windows should reboot into a 'Troubleshoot' screen (make sure you keep the shift key pressed whilst it restarts).
Does the 'Troubleshoot' screen appear?