Can I boot Windows from an HDD via USB? inaccessible_boot_device

Hi,

nunayer said:

Just used your thread to solve a problem cloning a Lenovo with UEFI.

What worked was using Samsung's Data Migration to clone to a Samsung SATA SSD in a USB dock, then make your registry change to the copy and use a Windows 10 setup USB to repair.

It then booted from the USB copy and I was able to use the already-installed Data Migration software to clone BACK into a newly installed Samsung M.2 SSD.

One interesting quirk: it booted fine from the internal, but when I tried to update Windows 10 to the latest build, I got an error complaining about Windows being installed on USB.

So I reversed the registry change, rebooted, and all's well.

Once again ... YOU ARE THE MAN! Thank you so much!

With all due respect that modus operandi to achieve what you wanted to achieve is really unnecessary.
Macrium Reflect Free allows you to backup existing installs as an image and restore it to whatever drive afterwards.

I also disagree with TS about how he created an external Windows system. It's not how that's done. It may work for a while but trouble's lurking around the corner.
Granted, this is an oldish thread but still.

Cheers,

jimbo45 said:

you can't use this method to actually boot a Windows 10 HDD from a USB unless it's a Windows to Go type of thing

jimbo45 said:

Windows to Go needs in any case either "certified devices" or Windows Enterprise 10 to install

fdegrove said:

There are still several software packages around that allow you to build a win to go install using any version of W7 to W10 on non-certified USB3.0 or higher devices.

You can boot any version of Windows from any external drive. USB key, USB drive, Thunderbolt drive, SD card etc - there have been tutorials on MacForums since 2 days after they started using Intel.

There is no voodoo about it and it is described fully by Microsoft here Windows To Go Step by Step - TechNet Articles or here Run Hyper-V Server from a USB Flash Drive

However, if you take a drive you were already running Windows on and try to boot it from external enclosure it will not work (while if you clean install it in the same external enclosure generally it will). The reason is that all drivers aren't loaded early by the kernel as if it tried to load every single possible driver your boot would take much longer.

If you want to boot your existing Windows install in another place (USB rather than SATA say) you may need to load those drivers earlier.

That is the point of this thread and the procedure works.

Thanks to both @carlossagan (OP) and @nunayer (for resurrecting it) - it helped me.

Hi,

However, if you take a drive you were already running Windows on and try to boot it from external enclosure it will not work (while if you clean install it in the same external enclosure generally it will). The reason is that all drivers aren't loaded early by the kernel as if it tried to load every single possible driver your boot would take much longer.

True but it won't be a Win to Go drive and if you go from external to internal it will likely crash or at best start a repair.
I know you know that and so do I @lx07.

My point being that sometimes people overcomplicate simple procedures. When you clone an internal drive to an extrnal one then you can expect trouble, right ?

Cheers,

fdegrove said:

if you go from external to internal it will likely crash or at best start a repair

I've never tried. I have installed on internal and then moved the disk to boot external many times. I think doing the opposite may just boot slower as it is loading unnecessary drivers.

fdegrove said:

My point being that sometimes people overcomplicate simple procedures.

Yup, I do.

For example @Bree said the other day solitaire was better on XP than Windows 7 version I was using. Rather than looking for a simple solution (download it in 5 minutes and see) I decided I had to find a XP ISO (this takes hours), install it to a VM (more hours), find the solitaire files required and copy them to my main PC and then try it. The end result was a waste of time as the XP games don't even work well with hiDPI screens - they look tiny.

Still - it is my hobby and I enjoyed the process :)

Hi,

Still - it is my hobby and I enjoyed the process

By all means please do.

The original postings from TS still create a grey area though. It's all well when you know exactly what you're doing and why you're doing it for. It's not a generic solution to those who do not know nor understand it though and there sits the risk of confusion and failure.

That said, I know well enough you have more than ample background to understand what I mean.

Cheers,

carlossagan said:

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.

Hi,
This thread/post is old enough on this great Forum, but I registered just to thank you very much for your great finding that does work like a charm.
Thank you!
Cheers

Does anyone have the command to change this using a batch file? I've cloned my ssd to USB and have been trying to figure out why it won't boot and this setting must be it.

Code:

reg ADD HKLM\SYSTEM\HardwareConfig\{8c2faede-eae0-7113-a972-2cf05dac9860} /v "BootDriverFlags" /t  REG_DWORD /d 14 /f

I do not know why, but I noticed that in some scenarios it seems better to replace 14 to 28 even if you don't boot from SD card.

Hey, thanks for this answer! I'm reading lots of threads now. I am unsure of one point. Is this registry mod done on my main Win10 registry or on the usb copy registry?