Windows Cumulative Update destroying the System Partition (EFI)? and causing infinite restart loop


  • On April 13 my laptop updated itself to the new Cumulative Update and I did not notice till it went "Updating PC, don't shut it off". I was like OH NO THE BLUE SCREEN DEATH UPDATE NOOOOO....

    The next time I started up my laptop it completed the update, then it shut off with the BSOD code 0x0....35 (inaccessible boot drive)

    I dove into the problem deeper.

    Somehow managed to get out of the infinite loop by inserting the install OS from a USB, then went to recover PC, tried everything, no restore point, no revert back to previous b4 update, nothing worked from the recovery options, same BSOD error code.

    After those tries, I pressed shift+F10 for cmd. Went into diskpart, checked my partitions, and there was no System partition. The update literally deleted the small System EFI partition...

    I tried this:


    list disk

    select disk 0

    list partition

    select partition 2

    shrink desired=260

    create partition efi size=260

    then error: YOUR DISK IS NOT GPT


    Checked around the internet and only found actual programs that needs an OS to install themselves on your laptop.

    Diskpart unfortunately can only do FORMAT and then convert MBR to GPT.

    I only need to create that small System partition, but it can't cuz the disk is not GPT type...

    Is there any way to convert my MBR to GPT using cmd WITHOUT LOSING DATA?

    Or any way to revert back the windows using an installer WITHOUT LOSING DATA?

    Or any way to fix this issue?

    I'm currently backing up my data by hand with cmd to my pendrive.


    No, Safe boot doesn't work, cuz no System partition.

    No, I cannot boot the windows in any way and cannot enter the GUI either.

    No, I don't want to lose my data.

    No, I cannot take the HDD out cuz it's a laptop.

    No, I don't have any recovery.

    No, I can't revert back to an earlier point either.

    Yes, I can only use CMD.

    Yes, I can only boot it with an USB hub with Windows Install on it.

    Saturday, April 15, 2017 2:19 PM

All replies

  • Hello,

    AFAIK, there is no way to convert MBR to GPT without losing data. I suggest you go ahead with data backup and then follow the conversion.


    Microsoft MVP (Windows and Devices for IT)

    Windows Insider MVP

    Windows Help & Support []

    • Marked as answer by KoppanySz Saturday, April 15, 2017 5:21 PM
    • Unmarked as answer by KoppanySz Sunday, April 16, 2017 10:13 AM
    Saturday, April 15, 2017 3:00 PM
  • Thanks, I'll do so I guess :/
    Saturday, April 15, 2017 5:21 PM
  • I had a spontaneous blue screen boot loop related to windows defender offline.  On another computer I reproduced it many times to find ways to potentially get out of the blue screen boot loop.  Each time I used the bootable iso to delete partitions and create an unallocated drive.  Then I reinstalled the operating system and reproduced the windows defender offline blue screen boot loop.  All approaches that were attempted using a windows 10 bootable iso windows troubleshooting menu failed.  Any reset attempt indicated that the drive was locked or the partition was missing or the step could not be performed.

    The only solution was to save files in a windows PE environment:

    Hard drive enclosures are inexpensive.  You can remove the notebook internal hard drive from its chassis.  The internal hard drive is then transferred to the hard drive enclosure and together they are connected by USB to your working computer.  You then may be able to recover files. 

    When I had the files saved it was performed at a Microsoft store in the windows PE.  The bios was changed from Legacy to UEFI.  The drive was sanitized.  The windows 10 1607 was reinstalled.  Drivers were reinstalled.  Files were reinstalled. 

    That did not however completely fix the problems.  The windows 10 version 1607 after its clean install now fails to update to version 1703.  I am working on troubleshooting that problem now.  The back up plan is to return the computer to the Microsoft store and have them save the files again and this time install version 1703.

    Also I learned that some things are gone unless you had prepared for a drive failure.  For example all of the browser bookmarks were gone.

    So consider giving the hard drive enclosure a shot if you are technically inclined or consider having a computer store backing up your files in a windows PE and then reinstalling windows 10 version 1703.  Be prepared to go to the computer manufacturers web site to install missed applications and drivers. 

    Saturday, April 15, 2017 8:32 PM
  • Actually, in 1703, there is a new utility that converts MBR to GPT without any loss of data:


    Whether it is of any help in this context I don't know.

    ________________ drahnier

    Sunday, April 16, 2017 4:24 AM
  • On one of my other threads someone had a very challenging problem and reported success with:

    I've never used it.  It may be worth a try.

    Sunday, April 16, 2017 7:46 AM