SOLVED Couldn’t install Windows 10 Technical Preview

Well today is two blog posts in a row 😀 Both covering Windows 10.

After my first issue I ran into another that had me stunned for a while.


“Couldn’t install Windows 10 Technical Preview.  Windows can’t be installed because this PC has an unsupported disk layout for UEFI firmware.  Please reboot and change the PC’s firmware to BIOS to allow Windows to setup to continue.”

I then looked into the log C:\$Windows.~BT\Sources\Panther\setupact.log

There I found the cause to this error:

CONX ConX::Compatibility::CSystemAbstraction::HostIsUEFIDiskLayout: Boot disk has ESP partition.
CONX ConX::Compatibility::CSystemAbstraction::HostIsUEFIDiskLayout: Boot disk does not have MSR partition.
ConX::Compatibility::CSystemAbstraction::HostIsUEFIDiskLayout: Boot disk does not have UEFI disk layout.

I didn’t seem to have a MSR partition.

A quick look using diskpart confirmed this. So i opened up some space on the disk using Disk Management and created the partition.


That sorted the issue and I’m writing this blog post from Build 10041


5 Responses to SOLVED Couldn’t install Windows 10 Technical Preview

  1. Magnun says:

    Tanks Man! this Work for me!

  2. Magnun says:


  3. Flamez says:

    I have a Sony Vaio touchscreen laptop with i7-3537U CPU, 64bits running on windows 8.1. Tried installing the windows 10 preview but at the last step it says restoring previous version of Windows. when it restarts it shows a blue window saying;


    The installation failed in the SECOND_BOOT phase with an error during MIGRATE_DATA operation.

    Please does anyone have this issue, or know how to solve it??

  4. Gregg Eells, P.E. says:

    After researching the failure of Win10 to upgrade on my Z87 1TB Windows 7 Home Premium PC, I ran across a possible answer to Flamez’s question. My system would get to 91% and reboot (the second reboot). Then without any error message at all, it said “Restoring previous Windows version” a lot of disk activity and I was back to Windows 7 with an error message in Windows Update of “Unknown Error – 8007002C-4000D,” which looks a lot like the code Flamez’s machine threw.
    When I partitioned the disk on this machine, I thought I was hot stuff by following a guide to remove the 100MB unseen partition that Win7 sets up when you do a clean install. The guide said that it was only used for BitLocker functions and if you were not going to use BitLocker there was no use to eat up 100MB of your drive. Well, little did I know that the 100MB partition allowed the hard disk on a UEFI BIOS equipped motherboard to form a GUID Partition Table (GPT), rather than a standard MBR partition setup. Apparently, Windows 10 REQUIRES a GPT drive on a UEFI MB for a complete install after Build 1511,10586.
    So if your disk is set up as an MBR disk rather than GPT, Win 10 will not install. To check the status of your boot disk (usually disk 0 or disk 1) use the Diskpart utility. Do the following:
    1. Click on the orb, and type in “cmd” in the Search programs and files box.
    2. CMD.exe should appear as the only choice – right click and Run as Administrator.
    3. You should be at /System32> – Type diskpart
    4. After a brief delay, you should be at a Diskpart prompt – Type “list disk” (without the quotes).
    5. Be sure to type “exit” at the diskpart prompt to end the diskpart session.
    You should see a listing of your drives (no partitions will be shown only physical drives). It should look like the following:

    DISKPART> list disk
    Disk ### Status Size Free Dyn Gpt
    ——– ————- ——- ——- — —
    * Disk 0 Online 113 GB 128 MB *

    Note the asterisk under the GPT column. This disk will probably accept and fully load Windows 10. But, if there is no GPT asterisk, your disk is set up as MBR (Master boot record) and Win10 may fail at the second reboot of the upgrade process.
    I recently loaded a clean install of Windows 7 onto a 2TB drive with a UEFI BIOS and did NOT remove the 100MB hidden partition. Win 7 loaded up fine and once I hit SP1 on Window Update, it was offering to upgrade to Windows 10 and did so without a hitch. My drive shows that it is a GPT setup, but the drive I have had a failure for the Win10 upgrade (at second boot – restoring previous windows version) shows no asterisk under GPT, hence it is MBR and Win10 failed to complete.
    All this is fully discussed at the Windows 10 Forums here:
    The diskpart instructions and screen shots are shown and on post #22 a link is given for a Microsoft guide on how to convert a disk to GPT. But, the guide says the disk must have no partitions on it, so you have to delete all partitions down to a low-level format stage to go forward. I have the feeling that if you reinstall Windows 7 or Windows 8.x and make sure the UEFI, rather than “Legacy” or some such is selected in the BIOS for disk management, it should create a GPT system disk when you reinstall and don’t eliminate the 100MB hidden partition. Try it and see with diskpart if you get a GPT disk. If not, use the link on post #22, which I have repeated here for convenience:

    This issue seems to only crop up when you have a UEFI BIOS (older non-UEFI PCs should not have a problem) and an MBR disk setup. I think Microsoft should add checking the GPT/MBR/UEFI drive status at the initial setup check to avoid this perplexing problem.
    I hope this discussion will help others who are having the problems I have experienced with Win 10 failing to complete the upgrade.

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