Windows 10: Can I boot Windows from an HDD via USB? inaccessible_boot_device

  1.    14 Aug 2015 #1

    Can I boot Windows from an HDD via USB? inaccessible_boot_device

    I have a Toshiba P55T-B5262 that came with a 1TB HDD containing 5 partitions:

    1.00 GB Healthy (Recovery Partition)
    100 MB Healthy (EFI System Partition)
    918.77 GB NTFS C: Healthy (Primary Parition)
    791 MB Health (Recovery Partition)
    10.75 GB Healthy (Recovery Partition)

    I upgraded the Windows 8.1 installation on C: to Windows 10.

    Then I split the 918.77 GB partition into:
    403.06 GB NTFS C: Healthy (Primary Parition)
    515.71 GB NTFS G: Healthy (Primary Parition)

    After doing the split everything still works fine and the computer boots into Windows 10 as it should and I have an extra partition at G: like I expected.

    Then I cloned all of the partitions except G: onto a 480GB SSD using EasUS Todo Backup.

    The resulting partitions on the SSD are:
    8 MB Unallocated
    1.00 GB Healthy (Recovery Partition)
    100 MB Healthy (EFI System Partition)
    434.36 GB NTFS C: Healthy (Boot, Page File, Crash Dump, Primary Partition)
    791 MB Health (Recovery Partition)
    10.75 GB Healthy (Recovery Partition)
    8 MB Unallocated

    After doing the clone I am able to still boot the computer from the original HDD just fine.

    I can also replace the HDD with the SSD and the computer boots into Windows just fine from the SSD.

    Either hard drive lets me boot into Windows and both work perfectly and I can see all of the partitions in the disk manager in Windows.

    However, when I boot from the SSD and I try to use the "Create a recovery drive" option in Windows it tells me that some files are missing and won't let me create a recovery drive. For some reason it can't see the recovery partition that was copied over from the HDD even though it's there and shows in disk manager.

    Both drives work fine to boot from, but Windows doesn't seems to recognize the factory recovery partitions on the cloned drive. When I go into advanced boot options for Windows with the SSD installed I see the startup settings (for safe mode, etc) but the recovery option isn't there like it is when I go into the advanced options when booting from the original HDD.

    Anyway, this led me to want to boot from my original HDD so that I could create a USB recovery drive, but I didn't want to keep taking all of the screws out of my computer to switch the hard drives, so I wanted to boot from the original HDD by plugging it via USB. So I put the original HDD into a USB encasement to try this.

    If I boot the laptop from the SSD and then plug in the original HDD via USB I can see all of the partitions in the disk manager and access the files from the two primary paritions so the drive works fine. Plus I can switch the SSD for the HDD and the laptop boots from the HDD fine, so it's bootable and the MBR and all that stuff hasn't been modified at all, it was simply cloned onto the SSD.

    But if I reboot the laptop with the HDD plugged in via USB the computer launches into automatic repair and then gives me a blue screen with inaccessible_boot_device as the error.

    The BIOS on the laptop is set to boot UEFI with USB first over the SSD, although I've tried it on CSM (the only other option) but with no luck.

    Every time I try to boot from the original HDD plugged in via USB I get inaccessible_boot_device. Startup repair doesn't fix it. And when I go into system restore from the startup troubleshooting screen, I see the restore points from the SSD NOT the ones from the HDD. So, the recovery partition on the HDD is kicking in and letting me see the system restore and reset / recovery options (unlike when I boot from the SSD) but I can't boot from it. If I put the HDD int the computer as normal it boots fine, but when I have it plugged in USB it gives me that error.

    I just want to be able to plug this working, bootable Windows hard drive into the PC it came with (which works fine to boot from when installed internally) and have the PC boot from it.

    As an experiment I plugged the HDD into a DIFFERENT laptop (a Dell I have laying around) and I changed the BIOS on that laptop to boot UEFI instead of legacy, the Dell actually boots Windows 10 from the external HDD. It runs an automatic repair first, then in the repair screen I chose "Exit and continue to Windows 10" and it booted the entire OS from the external HDD and everything worked fine. After it did the automatic repair the one time, now when boot the Dell laptop with the external HDD plugged in it will boot from the external HDD into Windows 10 perfectly.

    So, another laptop will boot from the external HDD and go into Windows 10, but the laptop the HDD came with won't boot from it.

    Does anyone have any ideas or have an idea what I might be able to do to fix this?

    The main thing I want to do is be able to boot the laptop into Windows 10 from the original HDD via USB instead of having to plug it in via SATA.

      My ComputerSystem Spec

  2.    14 Aug 2015 #2

    I figured it out, it was USB 3.0 drivers not being loaded

    Solved it!

    I booted up the other laptop using the external drive to get into the Windows 10 installation and I changed BootDriverFlags in the registry for the installation to 0x14 instead of 0. That forces the USB 3.0 drivers (all the ports on the Toshiba laptop are 3.0) to load early in the boot. They weren't being loaded early enough before, so the external drive couldn't boot since it was running over USB 3.0

    After doing that, I can plug the HDD into the Toshiba via USB and it boots from the external HDD, which is the original HDD that came with the laptop just in an external encasement.

    Now the laptop boots from the SSD that I cloned the HDD to and installed but I can plug the original HDD in at anytime via USB to boot from it instead.

    Now I have two separate installations that I can boot from, so I can create two totally different environments.

    The boot from the external drive is a little slower than normal, but after the initial startup and login (maybe 2 minutes total until the system "settles down" and is ready for use) everything runs pretty quick. Definitely fast enough to operate on and do most things.
      My ComputerSystem Spec

  3.    14 Aug 2015 #3

    And I can create a recovery drive

    Also, I'm able to create a recovery drive when I boot from the external HDD. So now I have a fully bootable recovery drive to reset the PC at anytime. In addition to a working cloned Windows 10 SSD installed and an external (or internal) bootable Windows 10 HDD that is also fully configured. Along with a Windows 10 system image backup on another external HDD that can be used for a fully restore to any other drive.
    Last edited by carlossagan; 14 Aug 2015 at 08:58.
      My ComputerSystem Spec


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