How to resolve Error 0x80240fff when installing Windows Insider Builds

Recently I was trying to update a Sony Vaio Fit 15E laptop from Windows Insider Slow Ring build 14931 to 14965 via Windows Update. The update would complete downloading and commence installing, but would fail during the multiple reboot process, causing the previous build to be restored.

After ensuring I had no SD cards inserted or USB devices attached, here are the steps I took to resolve it:

Defering Feature Updates

1. Open Settings.
2. Click Update & Security.
3. Click Advanced Options.
4. Check the Defer feature updates box.
5. Retry the update process.

That didn’t work, so I tried:

Running the Windows Update Troubleshooter

1. Open Control Panel.
2. In the View by: dropdown, select Small icons.
3. Click Troubleshooting.
4. Click Fix problems with Windows Update.
5. Follow the onscreen instructions to fix any problems that are found.
6. Retry the update process.

That didn’t work either, so I tried:

Deleting the C:\$WINDOWS.~BT folder

1. Open File Explorer.
2. Click the View tab.
3. Check the Hidden items box in the Show/hide ribbon section.
4. Navigate to the C:\ drive.
5. Delete the $WINDOWS.~BT folder.
6. Retry the update process.

That didn’t work either, so I tried deferring feature updates again and rerunning the update process, producing this error:

There were some problems installing updates, but we’ll try again later. If you keep seeing this and want to search the web or contact support for information, this may help: (0x800705b4)

So I tried:

Installing from the ISO instead

1. Download the latest Slow Ring ISO here. You’ll need to sign in 1st so the page knows you’re a Windows Insider.
2. Using WinRAR, 7-Zip, or a similar archive extraction tool, extract the ISO file to a folder.
3. Open the above folder.
4. Launch the setup file.
5. Set the installer to keep your apps, files, and settings and let it run.

That didn’t work either, so I tried deleting the C:\$WINDOWS.~BT again and trying to install from ISO as above. This time I got this error:

0x8007042B – 0x4000D The installation failed in the SECOND_BOOT phase with an error during the MIGRATE_DATA operation

Although this error might seem disappointing, it was actually encouraging because it was the 1st one I’d gotten that actually explained what the issue was.

Googling the error produced this excellent post by Andre Da Costa. I had to:

1. Do a clean boot (see link for instructions. It’s generally a good idea at all times – error or not – to enable clean boot before rebooting from your current build to install the new one. This will prevent existing startup processes from interfering with the installation.)
2. Disconnect the laptop from the internet (disable Wi-Fi, unplug Ethernet cable.)
3. Disconnect all non-essential USB peripherals, including mice if you have a working laptop touchpad.
4. Reboot.
5. Retry updating from the ISO files.

This finally fixed the issue.

Note that if you have any services or apps you’d prefer to run at startup, you’ll need to manually re-enable them via some combination of Task Manager, System Configuration, and Services.

I hate that the Insider build update process is this unreliable, but issues can be worked around with tenacity and thought.

Thanks to Microsoft employee /u/zac_l for his assistance on this Reddit support thread:

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