I am trying to run the upgrade from my Windows 8.1 Pro computer to Windows 10. It keeps telling me:

Setup has failed to validate the product key

This has happened when clicking "Upgrade" inside the Windows 10 Media Creation Tool and has also happened when running the installer from a flash drive. However, that flash drive did successfully install Windows 10 on another computer.

How can I fix this?

This computer is a Lenovo ThinkPad T530 which originally shipped with Windows 8 (basic), was upgraded to Windows 8 Pro, and then to Windows 8.1 Pro. When I run NirSoft's product key retrieval tool, it shows the original Windows 8 key stored by Lenovo in the BIOS as well as the Windows 8 Pro Upgrade key. Could it be that the upgrader has "decided" that these keys are not eligible for upgrade?

  • @ElTurner That's what I thought too. When I said that line about "not eligible", the key was that the upgrade checker doesn't know what to do with OEM key + upgrade key together - i.e. that it's just a case the current version of the tool can't handle.
    – Moshe Katz
    Jul 29, 2015 at 20:19
  • 1
    Have you double-checked you're upgrading to a compatible version? In other words, since you have Windows 8.1 Pro, you should be upgrading to Windows 10 Pro and should have chosen that version in the tool.
    – Reg Edit
    Jul 29, 2015 at 20:34
  • @RegEdit Yes, I am attempting to go from Windows 8.1 Pro to Windows 10 Pro.
    – Moshe Katz
    Jul 29, 2015 at 20:51

4 Answers 4


I read through the log files in C:\$Windows.~BT and discovered an error message that said:

Unable to create temp file in C:\Users\me\AppData\Local\Temp. The file already exists.

(That's not the exact wording, but it's pretty close. I'm typing this on my other machine while watching the installer run.)

I ran Disk Cleanup on the drive, which cleared out the Temp folder and the downloaded/unpacked installer files (in C:\$Windows.~BT and C:\$Windows.~WS), then started the installer again and had no trouble.

  • i had bad sucess with esd file from microsoft.com but the esd file in C:\$Windows.~BT worked so you can try using ESD Decrypter and make a iso of that one
    – nwgat
    Jul 30, 2015 at 4:59
  • @wiak - You could also sip the problematic ESD files and just download the .iSO
    – Ramhound
    Jul 30, 2015 at 16:27
  • i did it before the iso was around, worked out in the end
    – nwgat
    Jul 30, 2015 at 18:31
  • 1
    Downvoter: care to explain?
    – Moshe Katz
    Aug 5, 2015 at 18:35

None of the other answers worked for me, though Moshe Katz's answer did point me to the log files. Under C:\$Windows.~BT\Sources\Panther there are two log files, including an setuperr.log which indicated to me that it was in fact a license key issue. This did cause me a little confusion because I was never prompted to enter a key; I suspect Setup was attempting to autoactivate using the Windows 7 key or was looking for a Windows 10 OEM license in the BIOS.

I opened an admin command prompt, browsed to C:\ESD\ where the media creation tool stores its files, and I ran setup /pkey xxxxx-xxxxx-xxxxx-xxxxx-xxxxx using the retail product key we purchased and Setup worked perfectly.

  • Your solution to run setup.exe /pkey xxxxx-xxxxx-xxxxx-xxxxx-xxxxx also worked for me, thank you Jul 31, 2018 at 22:43
  • Thanks. Mine was looking for a 'D' drive. weird...
    – vr_driver
    May 25, 2020 at 7:01

Had the same problem when upgrading from Windows 7. The solution was to temporarily remove the machine from domain.

  • Turns out the group policies were a bit broken, and resetting the Default domain policy fixed the problem.
    – ender
    Aug 1, 2015 at 18:55

Had same issue - below steps helped me to finish successful upgrade from Windows 8.1 to 10 worked
1. Run disk cleanup utility https://support.microsoft.com/en-us/help/17421/windows-free-up-drive-space
2. Then (it can take a long time to execute):

Press Windows key + X
Click Command Prompt (Admin)
Type each command at the prompt then hit enter after each scan is complete)
Dism /Online /Cleanup-Image /CheckHealth
Dism /Online /Cleanup-Image /ScanHealth
Dism /Online /Cleanup-Image /RestoreHealth

(source https://www.groovypost.com/howto/10-things-check-before-installing-windows-10/)
3. Additionally turned off antivirus when I started win10 upgrade

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