Optimize Drives – PortableBaseLayer

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I happened to open the “Defragment and Optimize Drives” app to see if my C:\ drive had been optimized on a monthly basis yet and I found an additional line for PortableBaseLayer. I’ve never seen this before on this screen. See the first attachment.

I expanded the line to see more info about PortableBaseLayer and the 2nd attachment shows what is there.

How did this get here? What is it for??

I do NOT have Windows Sandbox turned on.

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It does appear to belong to Windows Sandbox:

PortableBaseLayer also shows up in the defragmenter (“Optimize drives”) window as a virtual hard disk.
…
It’s a mounted virtual drive (.vhdx) which is used by the Windows Sandbox feature.

What is PortableBaseLayer Partition in Windows 10 Disk Management

You don’t have Windows Sandbox enabled at Control Panel, Programs & Features, Turn Windows features on or off?

(I have Windows Sandbox and also have the same PortableBaseLayer in Optimize Drives.)

Most documentation says it should be removed when Windows Sandbox is disabled, but one Microsoft Answer claims the only way to delete it is to perform an in-place upgrade (repair install):

After removal of sandbox, portablebaselayer partition stays

Windows 11 Pro version 22H2 build 22621.1778 + Microsoft 365 + Edge

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No, I don’t have Windows Sandbox turned on.

But, recently, I DID install Windows Defender Application Guard at the link at Settings|Windows Update & Security|App & Browser control|Isolated browsing|Turn on Application Guard. And then, at Windows Features, I checked the box for Windows Defender Application Guard. Application Guard is supposed to “open Edge in an isolated browsing environment to better protect the device and data from malware,” according to the information at the link. At Isolated browsing, I changed the settings to ON for Save data, Copy & paste, Print files, and Camera & Microphone.

I am on version 1909. Is the existence of this virtual drive going to interfere with updating to 2004 or 20H2?

I think, but am not sure, that the virtual drive can be removed by reversing the process I went through to install the Application Guard, turn it on, and set Windows Features for it.

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b

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Yes, PortableBaseLayer does seem to be needed by Application Guard too:

The PortableBaseLayer virtual partition is important when using the Windows Sandbox or the Windows Defender Application Guard protection feature.

Hyper-V partition write protected and unremoveable

I had Windows Sandbox and Application Guard enabled long before 2004/20H2 and the PortableBaseLayer did not cause any issues with updating to those versions.

Windows 11 Pro version 22H2 build 22621.1778 + Microsoft 365 + Edge

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WCHS

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b wrote:

Hyper-V partition write protected and unremoveable…

Just to see what would happen if I turned OFF Windows Features|Windows Defender Application Guard and then restarted:

The PortableBaseLayer doesn’t show up any longer in Optimize Drives nor in a run of Diskmgmt.msc

Afterwards, I checked Windows Security|App & browser control|Isolated browsing. The link reads “Install Windows Defender Application Guard”, so turning off the Feature uninstalled it as well.

I’m running Windows 10 Pro, version 1909.

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b

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b wrote:

one Microsoft Answer claims the only way to delete it is to perform an in-place upgrade (repair install)

Device Manager -> Disk drivers -> Uninstall

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