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Powering Thru Windows 10 Dual Boot Mishaps

One of my test PCs is set up for dual boot, because I use it for both Windows 10 1607 (Current Branch) and Insider Preview versions. After upgrading to Build 15063 earlier this week, I noticed that the installer had knocked out BCD entries for both Macrium Reflect System Recovery and the 1607 OS. I turned to my normal go-to tool for handling BCD stuff: NeoSmart Technologies EasyBCD 2.3. But instead of fixing my problem, I found myself powering through Windows 10 dual boot mishaps both various and mysterious.

After using the Add New Entry button to restore entries for both Macrium Reflect System Recovery and my “other OS boot” ( labeled Win10 1607 in the screenshot) I expected to be back in action. But alas, when I attempted to access the latter boot option, I was treated to an error screen instead. It informed me that because it couldn’t find the file named “winload.efi” at the designated location it couldn’t boot, either. Yet that file was clearly present where it was supposed to be, in the %Windir%\system32 folder on the target drive.

Windows 10 dual boot mishaps

To all appearances, these BCD entries all looked correct. But I couldn’t boot to my “other OS” successfully.

How I Found Myself Powering Thru Windows 10 Dual Boot Mishaps

What I did next has to be what caused the ensuing round of difficulties. Realizing something was wrong with my BCD data, I turned to EasyBCD’s “BCD Backup/Repair” tools, then elected the “Re-create/repair boot files” option.

Windows 10 dual boot mishaps

However, when I tried my next reboot, I found the PC stuck in the UEFI shell, unable to boot anything. I even had trouble accessing the motherboard BIOS to force an alternate boot to a repair UFD. The only way I was able to fix my problem was to walk through a somewhat tortuous and time-consuming series of steps:

  1. I had to disconnect all the internal drives except for 1 boot drive at a time.
  2. I had to boot to the Macrium Recovery UFD, and use its boot repair tool on each drive individually. This restored each one to bootable condition.
  3. After getting each boot drive working, I performed a disk cleanup and made a boot image backup using Macrium Reflect (in case the same problem recurred).
  4. Once each one would boot by itself, I used EasyBCD to add a new boot entry while booted into Insider Preview to accommodate the 1607 OS version.
  5. I used Macrium’s tool in its “Other Options” menu to return the recovery partition to the boot menu as well (“Add Recovery Boot Menu Option…”).

I have to believe my error came from the confluence of Macrium- and EasyBCD-based changes to the BCD data. Using Macrium to make Macrium-related changes, and EasyBCD to make general BCD additions (the second OS from my Insider Preview boot) fixed the problem. But what a painful 3 hours it took me to put things back to rights! I hope others in the same boat can learn from my innocent and unthinking mistake, and avoid Windows 10 dual boot mishaps altogether.

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