Any way to mod a Windows 10 iso so it'll install on an MBR partition?

teckneeculler · 09 Jul 2024

Megahertz: Thanks, but if I understand you correctly, I'm not intending to install W10 on the USB drives. They're just unimportant data caches.
SIW2: 'Or you could convert your 465GB NVMe Samsung SSD 970 disk to gpt partition style. It is quite easy.' This would definitely be my preferred option but how to achieve this? Seems to me I'd need to backup the entire drive contents (possibly first removing the Q partition to simplify the operation), convert the SSD to GPT, using Diskpart or whatever, then copy back the original contents. I guess I could do that with Macrium.

SIW2 · 09 Jul 2024

If you have winre enabled, disable it first at admin cmd propmt

reagentc /disable

Then I would use the free version of diskgenius. Create the boot media, boot it up and run it from there.

1. convert the evo 970 disk to gpt

2. convert the 499mb partition to esp partition

3. use bcdboot command to create the boot entry

takes only a few seconds to do each of the above.

I have done it many times, without any data loss

you can borrow my boot media . I think I included diskgenius
23v7.iso

extract the 23v7.iso to usb stick using something like usb7ice

Usb7ice.zip

Any way to mod a Windows 10 iso so it'll install on an MBR partition?-usb7ice.jpg

- - - Updated - - -

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1. convert disk to gpt

Right-click the MBR disk you want to change partition table type and choose "Convert To GUID Partition Table".

then Click "Save All" button from toolbar and click "Yes" to save changes to the disk

Convert Partition Type Between MBR and GPT Without Data Loss

2. convert 499mb partition to esp partition

the easiest way is delete the 499mb partition. Rt click the 499mb partition and select delete current partition ( then click save all )

rt click the 499 unallocated space and select "create esp/msr" accept the sizes and offsets it offers . Then click save all ( it will ask if you want to format esp partition immediately, say yes ).

3. then it is just populate the esp partition with the boot critical files using bcdboot command

at cmd prompt

bcdboot whatever is the windows partition letter as seen from winpe:\windows /s device path /f all

for example

bcdboot d:\windows /s \Device\HarddiskVolume6 /f all

you can find the device path of the esp partition in diskgenius main window on the right and copy and paste it into the command

Any way to mod a Windows 10 iso so it'll install on an MBR partition?-dg-devicepath6.jpg

teckneeculler · 10 Jul 2024

SIW2: Wow, that's excellent. If I can manage to get my head around the method, it'll solve my problem. Thanks so much.

Edit: Looks like WinRe is enabled. I had no idea. Duh.

Any way to mod a Windows 10 iso so it'll install on an MBR partition?-winre.jpg

Neither did I really know that an 'esp' is...
The EFI (Extensible Firmware Interface) system partition contains the boot loaders, boot managers, or kernel images of installed operating systems (which are typically contained in other partitions), device driver files for hardware devices present in a computer and used by the firmware at boot time, system utility programs that are intended to be run before an before an operating system is booted, and data files such as error logs.
Thanks mate, got the iso. I'm on a voyage of discovery

Volume Z · 10 Jul 2024

It's so much easier. Of course you are not intending to install Windows 10 on the USB drives. It's not us who are getting you wrong. It's you who is getting us wrong. Your USB drive (drive U) is marked as active, so it is BIOS (MBR) bootable. There is a non-EFI entry for the device existing in your UEFI, and all you need to do is find it. There are no permanent changes to make as this is a one time choice.

I can easily reproduce the error you are seeing by booting a Setup the wrong way:

Any way to mod a Windows 10 iso so it'll install on an MBR partition?-cannot-installed.png

Megahertz07 · 10 Jul 2024

teckneeculler said:

Megahertz: Thanks, but if I understand you correctly, I'm not intending to install W10 on the USB drives. They're just unimportant data caches.

No, you undestood all WRONG. Read it again.

SIW2 · 10 Jul 2024

diskgenius is under the startmenu in the disktools folder

Any way to mod a Windows 10 iso so it'll install on an MBR partition?-23h2-diskgenius.jpg

teckneeculler · 10 Jul 2024

Thanks SIW2. I'll take my time and work slowly through this.

teckneeculler · 27 Jul 2024

SIW2: Sorry about delay, I've been trying to work out a backup method for my main system disk in case anything went wrong. I think I now have that covered and I'll explain later.
I did a trial run of your ISO and managed to find the relevant areas of Disk Genius. Apart from a few minor queries I think I understand it. When you say 'at command prompt' I assume you meant 'run cmd from the taskbar shortcut' in your booted app. Also, you mentioned winpe here 'as seen from winpe:windows /s device path /f all'. I assume you didn't mean to use winpe but simply find the device path in Disk Genius. Which would make the path, in my case, bcdboot j:\windows \Device\HarddiskVolume9 /f all.
Last, I noticed when Disk Genius opens a message appears at top: 'Disk Genius v.5.5.1.1508x64. New version found: v.5.6.01565. Release notes....' Is that relevant?

teckneeculler · 31 Jul 2024

Well, it worked - eventually. Had a few frantic moments when my keyboard refused to make a \ backslash, but found that Right\Alt + backslash fixed it. So my main SSD (or, fortunately, a copy thereof) is now GPT. But, durn, a large problem now with my W7 Ultimate.
So back to my original MBR and I'll run W10 on a separate SATA HDD. Much thanks to SIW2 and to everyone else who commented.