Go to REGEDIT
To determine whether the Power button appears on your Start screen, you need to fire up the Registry Editor (use Smart Search and search for regedit) and then navigate to HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\ImmersiveShell and then expand that node so that you can see its sub-keys.
Now, right-click on ImmersiveShell and choose New and then Key from the pop-up menu.
Name it Launcher.
Now, with Launcher selected, right-click in the right pane of the Registry Editor and choose DWORD (32-bit) Value. Name that value as Launcher_ShowPowerButtonOnStartScreen.
If this value is set to 0, the Start screen-based Power button will be disabled and will not appear.
To make the Power button (re)appear, (re)set this value to 1.
You will need to reboot each time you make this change.
