Help Making existing windows 11 drive bootable via USB on another PC

I upgraded my PC drive to a new/faster SSD. I want to use the old drive as an emergency bootable drive in case my new drive has issues (which it currently does).

When I set the boot config in BIOS to boot to the external USB Thunderbolt device, I get BSD with Inacessible Drive error. I formatted my EFI partition to FAT32 and used BCDEDIT to create new BCD records, but wondering if the issues is the fact that the BCE records specify the partitions by drive letter. Yes, these are drive letters E: and F: now as I am booted into Disk 0. But when I boot into the External USB, won't these drives be different (i.e. the boot loader will be C:, not F:). So is this why I get Inaccessible error as it can't find E: or F: when booting into this External USB drive?

If so, what do I update the Device pararmeters to in the BCD to point to correct partitions when booting into this drive? I would think you'd have the Device specified as some Id that uniquely identifies the drive, not a relative drive Letter that changes.

Am I on the right path? :)

The Subject line suggests 2 computers but the first line suggests only one computer.

I've never had success booting Windows from a USB drive, either HDD, SSD or Thumb drive. I do use Linux on bootable USB Thumb drives.

Berton said:

The Subject line suggests 2 computers but the first line suggests only one computer.

I've never had success booting Windows from a USB drive, either HDD, SSD or Thumb drive. I do use Linux on bootable USB Thumb drives.

Click to expand...

Yes, 2 PCs. I have one as my main PC. I cloned that SSD to put in an external Thunderbolt drive so in case the original is corrupted, I can then go to my 2nd, backup PC and boot from the Thunderbolt drive (the clone) to continue to be able to perform my work while I work on the the original corrupted one.

I actually have multiple clones and can boot from one of them, but the on in the thunderbolt enclosure is the one I'm struggling with.

So is this why I get Inaccessible error as it can't find E: or F: when booting into this External USB drive?

Click to expand...

bcd store references the disk and partition id. Letter is an alias for your convenience.

To boot disk 2 from current Boot Menu Options
from CMD Prompt (Admin) - Type > bcdboot H:\Windows /addlast

under Current Booted OS (Disk 2 Pictured) - insert the USB Drive and type
bcdboot H:\Windows /s F: /f UEFI

those are the Drive letters
Once booted from USB Drive the Drive Letter will change to C

KYHI said:

To boot disk 2 from current Boot Menu Options
from CMD Prompt (Admin) - Type > bcdboot H:\Windows /addlast

under Current Booted OS (Disk 2 Pictured) - insert the USB Drive and type
bcdboot H:\Windows /s F: /f UEFI

those are the Drive letters
Once booted from USB Drive the Drive Letter will change to C

Click to expand...

@KYHI

You might also need to alter a regkey - portableoperatingsystem to '0' if you wish to update the relevant OS to a new windows version.

Also to initially install the OS to a portable drive (new install) use dism /ApplyImage to install it. To use a local account select work or school computer and then at sign in options choose join a domain. - You don't even have to have one. Then install carries on with a local account.

Note to "clone" an existing OS to a bootable portable drive simply use something like Macrium to image /restore or clone to the device -- then from install media / other system /winpe etc boot into command mode and re-install the bootloader to the device as er previous post. No need for paid versions of software to create "Windows2GO" type systems.

The device with the other system(s) on it doesn't need to be efi either -- only the "original" boot disk that contains the boot menu. In fact it's probably better NOT to have the 2nd disk as efi otherwise when booting windows -- especially if you have multiple systems on the external device you'll get presented with the boot meny initially and again when you are booting your desired OS.

If you have more than 6 then you will be offered another page and so on -- not sure though what the limit is even if there is a max number. I'm using a 1.2 TB external nvme stick in a usbc adapter -- not much physically bigger than a large usb thumb drive and much faster and more resilient too. I'm using this on a laptop where the internal disk runs a Linux system.





cheers
jimbo

SIW2 said:

bcd store references the disk and partition id. Letter is an alias for your convenience.

Click to expand...

Ok, cool, so it is just dumming that view down for me and showing the current drive letter that represents the underlying partition.

jimbo45 said:

@KYHI

You might also need to alter a regkey - portableoperatingsystem to '0' if you wish to update the relevant OS to a new windows version.

cheers
jimbo

Click to expand...

That PC will boot from another external USB-C NVME drive I have so I think this must be set or doesn't need it.
The issue is with this Thunderbolt NVME SSD enclosure. It was set as a MBR, I thought that was the issue, so converted it to GPT. Then added the boot records.

I'd prefer not to edit the boot manager to add this, but would rather just change the PC's bios to boot from it as I have several backup PCs that get shared around, so not sure which one will be available at the time I may need it. i.e. want this external drive to be as portable as possible.