I am trying to install/upgrade Windows Pro 8.1 to Windows 10 through setup.exe from C:\$Windows.~BT. But installer tell me that boot.wim file is missing.

In update history logs I can see that update to windows 10 failed many times since july 29th.

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1 Answer 1


I had the exact same error while I wanted to upgrade from Windows 8.1 to Windows 10. My solution was the following:

  1. Log in as an administrator.
  2. Press Windows+R, enter regedit and press enter to open the registry editor.
  3. Locate the registry key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\OSUpgrade (if it's missing, create it)
  4. Create a new DWORD (32-bit) value, call it AllowOSUpgrade and set its value to 0x00000001.
  5. Restart the control panel, browse to "Windows Update" and search for updates (if the button from step 6 is not already there).
  6. Now, a button with Getting started should appear. Click on it and follow the instructions to install Windows 10.

Source: http://answers.microsoft.com/en-us/windows/forum/windows_10-windows_install/windows-update-installation-failure-80240020/d695e827-9774-4e10-8972-df8d51a7bb51

  • Didn't work for me because that registry already has that value (0x00000001).
    – GreenGiant
    Jun 20, 2016 at 18:50

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