Windows 10 Boot Manager on Previous SSD

Discussion in 'PC Hardware, Software and Displays' started by sir doris, Nov 29, 2020.

  1. sir doris


    May 9, 2002
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    I think I know the answer to this and it's to reinstall Windows, but I'm just hoping someone knows different.

    My system had 2 SATA SSD's; a 250GB (Boot drive) and a 1TB drive. I then added an M.2 and installed Windows 10 on it as I wasn't sure I was ready to wipe the 250GB and remove it.

    Every time my PC boots I can choose which version of windows 10 I boot into (M.2 or 250GB SATA).

    I am now happy I have everything I need of the 250GB drive and last night I removed it, unfortunately the system now won't boot, presumably because the Windows Boot Manager is on that drive.

    With the Windows 10 USB stick I've tried to repair the M.2 installation but that down't work, I've also tried to reinstall windows over the top of the M.2 installation but that doesn't work either as it can't create the partitions required.

    Anyone got any ideas, before I delete the existing M.2 partitions and start over?
  2. orangpelupa

    orangpelupa Elite Bug Hunter
    Legend Veteran

    Oct 14, 2008
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    You can use bcdedit to manually add the boot manager entries.

    Been years since I done that tho, so I don't remember how to do it.

    Nowadays probably there are easy to use gui
    sir doris likes this.
  3. Silent_Buddha


    Mar 13, 2007
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    You can also automate it. Macrium Reflect can fix this although the last time I needed to do this (around 2017) the partitions on the boot drive ended up being a little messy. It still works fine, however. I could go through one of DmitryKo's posts about fixing the partitions and whatnot for the boot drive, but I just don't have time at the moment (there's never enough time).

    It's also possible that Macrium Reflect has fixed this as it was mostly due to Windows 10 and new MB's requiring UEFI boot for NVME drives. I switched from a SATA SSD to NVME when I upgraded to a Ryzen 1600x back then and I wanted to keep my existing Windows install. Cloned the drive fine, but UEFI boot needed more than what the previous BIOS boot required.

    Thankfully, Macrium Reflect (free) was able to get things working.

    Unknown Soldier likes this.
  4. Unknown Soldier


    Jul 28, 2002
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    Thanks, going to be doing my upgrade soon so will check this out.
  5. DmitryKo


    Feb 26, 2002
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    55°38′33″ N, 37°28′37″ E
    You don't seem to have a Windows Boot Manager partition on your 1 TB drive - therefore you will need to add EFI System and MSR partitions at the start and a Windows Recovery Environment partition at the end, and copy the necessary UEFI boot files.

    You will need to use a free disk partitioning utility, like Paragon Partition Manager, to non-destructively resize your current Windows partition (standard DiskPart can only shrink or grow partitions towards the end, but it cannot free the space at the beginning and relocate the MFT).

    First ensure that you have a GUID Partition Table (GPT) disk and convert from MBR disk if necessary, as NVMe disks require UEFI boot and GPT-style partitions. Resize the Windows partition to free 116 MB at the start o and 650 MB at the end, then create a 100 MB EFI System Partition (ESP) and a 16 MB Microsoft Reserved (MSR) partition at the start of the disk, and a 650 MB primary partition for the Windows Recovery Environment (WRE) at the end of the disk.

    Add temporary drive letters for ESP and WRE partitions and format them with FAT32 and NTFS filesystems respectively (you can either run DiskPart commands, or use the Paragon Partition Manager GUI to achieve this). Then run the BCDBoot utility to copy the Boot Manager files from the Windows system folder and create the default Boot Configuration Data (BCD) store on the ESP partition.

    Finally locate the recovery image a (WINRE.WIM) in the system folder (or use 7-Zip file archiver to extract them from a Windows 10 ISO image) and copy it to the WRE partition at the end of the disk. Put a blank ReAgent.xml there and run ReAgentC utility to recreate the BCD entry for the Recovery Environmen and enable it. Set the attributes for the WRE partition and remove temporary drive letters (with either DiskPart commands or Paragon Partition Manager GUI).

    More details can be found in this post and this TechNet article. (Caution: do not run the example partitioning scripts on your existing Windows 10 disk, since they contain the DiskPart clean command - you don't want to ever use it on your exising Windows disk, as this will erase all partitions).
    #5 DmitryKo, Dec 12, 2020
    Last edited: Jan 14, 2021
    Silent_Buddha, Kej and Rootax like this.

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