How to stop the Windows Insider update from breaking your Windows Sandbox

A Windows Insider update is causing trouble for the new Windows 10 Sandbox feature in the May 2019 Update. Here's how to prevent it or resolve it.

Windows 10 May 2019 Update: Everything you need to know

Those of you who've updated Windows 10 with the May 2019 Version 1903 Update or had been using the Windows Insider version earlier this year may have started playing with the Windows Sandbox. Available in Windows 10 Pro and Enterprise, the new Sandbox feature offers you a clean, barebones virtual Windows environment in which you can install and run unknown, untested, and potentially unsafe software without it affecting the rest of your system. Sounds good, but there's a hiccup, at least for those who do participate in the Windows Insider program.

Released on May 14, Windows 10 Insider Preview Build 18362.113 is aimed at all Windows Insider users, hitting the Slow, Fast, and Release Preview rings. But the build creates a glitch with the Windows Sandbox as well as with the Windows Defender Application Guard. Try to open the Sandbox, and it may not launch, triggering an error code of 0x800705b4, according to a Microsoft support document.

How can Windows Insider users get past this problem? First, you'll want to check to see which Insider Preview build is installed on your computer. Open Settings, go to System, and select the About setting. Scroll down the screen to the section for Windows Specifications to check your current build (Figure A).


Figure A

If you haven't yet installed Preview Build 18362.113, you'll want to stop the updates for now, which you can do one of two ways. Go to Update & Security and select the setting for Windows Insider Program. Turn on the switch to Stop getting preview builds (Figure B).


Figure B

Alternatively, stay in Update & Security, go to Windows Update, and select the option to Pause updates for seven days. With the latter option, you'll just need to keep an eye on the updates to make sure Preview Build 18362.113 doesn't get through.

If you have already installed the problematic preview build, Microsoft does suggest a Registry hack that you can implement as a temporary workaround (Figure C).


Figure C

Open the Registry using a local admin account and navigate to the following key: [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Containers\CmService\Policy].

Create the following two values:

Restart your computer and see if you can now launch the Sandbox.
In its support document, Microsoft said that it's working on a resolution and will provide an update in an upcoming release.

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By Lance Whitney

Lance Whitney is a freelance technology writer and trainer and a former IT professional. He's written for Time, CNET, PCMag, and several other publications. He's the author of two tech books--one on Windows and another on LinkedIn.