In testing Windows 8.1 Update 1 on a wide range of PCs over the past few months, I've seen some interesting behaviors, including a few I can't yet explain. But here's a slightly more ordinary behavior that you can in fact toggle on or off in Update 1: That Start screen-based Power button.

If you read my Windows 8.1 Update 1 review, you know that there is some confusion about the Power button on the desktop, and for a good reason: You won't see it on every system. Microsoft tells me it's tied to an internal setting called the Power Platform Role that PC and device makers must set accurately in order to obtain the Windows logo.

If this setting is configured as "Slate," the button will not appear, because it would be too easy to tap accidentally and tablet users are comfortable with the edge-based UIs.

If it is set to "mobile device," as a laptop or Ultrabook would be, the button will appear.

Naturally, some people with tablet-type systems want this button. A bit less expectedly, I've also heard from a growing crowd of Windows 8 purists who are not particularly interested in this change, and they would like the Power button removed.

Good news. I can accommodate both groups.

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.

Thanks to Tero Alhonen for helping me with this.

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