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Guide: MultiBooting UEFI

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On the Win 10 installer partition page, after deleting the intended partition and recreating the required Win 10 partitions, reformatting the NTFS partition, and clicking 'Next', I kept getting the error 'we couldn't create a new partition or locate an existing one. For more information see the set up log files'.

I tried the same by just deleting my intended partition and clicking 'next' as the guide suggested to, and that also failed. It got stuck on copying files 0% then stated I would have to start the install process again. Doing that, I could see Windows had created the required partitions but it couldn't install onto them, as above.

I believe Win installer is expecting an MBR partition table and when it finds a GPT one on the target drive it doesn't work. My drive was formatted to GUID. Is there any way of booting up the installer in GPT mode not MBR mode? I am assuming worse case I can reformat this drive or a dedicated Windows drive as MBR.

I tried using an install DVD made from the latest Win 10 ISO and also from USB (formatted as GUID/FAT32, made with Rufus v3.8 and another attempt with v2.18). Neither was detected by BIOS until I enabled CSM Support. And even then, the DVD failed as described above whilst the USB stick did not boot up at all (either from BIOS or Clover). I assume I need to try again using a USB created using the MS Media Creation Tool when I have access to a Windows 10 PC (I wiped my existing Win 8.1 drive lol).
 
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Going Bald

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On the Win 10 installer partition page, after deleting the intended partition and recreating the required Win 10 partitions, reformatting the NTFS partition, and clicking 'Next', I kept getting the error 'we couldn't create a new partition or locate an existing one. For more information see the set up log files'.

I tried the same by just deleting my intended partition and clicking 'next' as the guide suggested to, and that also failed. It got stuck on copying files 0% then stated I would have to start the install process again. Doing that, I could see Windows had created the required partitions but it couldn't install onto them, as above.

I believe Win installer is expecting an MBR partition table and when it finds a GPT one on the target drive it doesn't work. My drive was formatted to GUID. Is there any way of booting up the installer in GPT mode not MBR mode? I am assuming worse case I can reformat this drive or a dedicated Windows drive as MBR.

I tried using an install DVD made from the latest Win 10 ISO and also from USB (formatted as GUID/FAT32, made with Rufus v3.8 and another attempt with v2.18). Neither was detected by BIOS until I enabled CSM Support. And even then, the DVD failed as described above whilst the USB stick did not boot up at all (either from BIOS or Clover). I assume I need to try again using a USB created using the MS Media Creation Tool when I have access to a Windows 10 PC (I wiped my existing Win 8.1 drive lol).
Where did you get the Win10 iso? Best to get it from Microsoft: https://www.microsoft.com/en-us/software-download/windows10ISO
 
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When doing it again earlier today, I made sure to start the Windows installer DVD from its EFI folder by selecting the relevant 'save and exit' option in the BIOS so it would be running in UEFI mode. I tried both the Win 10 DVD and Win 8.1 DVD (it's a Win 8.1 Pro licence) in the same way. I was able to do this with or without CSM Support set in the BIOS. However, the net result was still the same errors at the installation stage.
 

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When doing it again earlier today, I made sure to start the Windows installer DVD from its EFI folder by selecting the relevant 'save and exit' option in the BIOS so it would be running in UEFI mode. I tried both the Win 10 DVD and Win 8.1 DVD (it's a Win 8.1 Pro licence) in the same way. I was able to do this with or without CSM Support set in the BIOS. However, the net result was still the same errors at the installation stage.
When you boot the Win10 installer, hit your function key to select a boot device and select the Win10 install USB with UEFI in the list title.

Are you installing Win10 to its own drive? If you are, suggest you try using diskpart to clean and format your drive.
Boot your install Win10 USB and at the installation screen, instead of selecting a partition, hold shift+10 to open a command window.
type and hit enter the following lines - // is comment only - do not type

disk part
list disk //should come back with a list of disks - if more than one is connected make sure you get the right one!
select disk * //where * is the number of the disk - it will come back with disk * is now the selected disk
clean //disk part will now clean the drive - when done will say it succeeded in cleaning the disk
convert GPT
create partition efi size=200 format fs=fat32 label="EFI"
create partition primary format fs=NTFS
exit
exit

Now select the primary partition in the installation window and click on Next. The Win10 installer should be able to complete its task.
 
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When you boot the Win10 installer, hit your function key to select a boot device and select the Win10 install USB with UEFI in the list title.

Are you installing Win10 to its own drive? If you are, suggest you try using diskpart to clean and format your drive.
Boot your install Win10 USB and at the installation screen, instead of selecting a partition, hold shift+10 to open a command window.
type and hit enter the following lines - // is comment only - do not type

disk part
list disk //should come back with a list of disks - if more than one is connected make sure you get the right one!
select disk * //where * is the number of the disk - it will come back with disk * is now the selected disk
clean //disk part will now clean the drive - when done will say it succeeded in cleaning the disk
convert GPT
create partition efi size=200 format fs=fat32 label="EFI"
create partition primary format fs=NTFS
exit
exit

Now select the primary partition in the installation window and click on Next. The Win10 installer should be able to complete its task.

Thanks very much for all the tips. I was trying to install Win 10 onto the same drive as an APFS container. I've previously only installed Windows on its own SSD on a Hackintosh (did it with Boot Camp on same drive on my old iMac which was easy), but on my current machine I'm trying to put all OSes onto my new SSD as it is faster than my other SSDs. Worst case I will put Win 10 on its own SSD. Cheers.
 

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Thanks very much for all the tips. I was trying to install Win 10 onto the same drive as an APFS container. I've previously only installed Windows on its own SSD on a Hackintosh (did it with Boot Camp on same drive on my old iMac which was easy), but on my current machine I'm trying to put all OSes onto my new SSD as it is faster than my other SSDs. Worst case I will put Win 10 on its own SSD. Cheers.
Shrink your APFS container by the amount you want to dedicate to Win10. Create a partition in that space format FAT with Mac disk utility. At the Win10 install screen select this partition and delete it. Select this free space, click on create new partition and format NTFS. Install Win10 to this partition.
 
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Shrink your APFS container by the amount you want to dedicate to Win10. Create a partition in that space format FAT with Mac disk utility. At the Win10 install screen select this partition and delete it. Select this free space, click on create new partition and format NTFS. Install Win10 to this partition.

I can't get any of the above methods to work. I tried it on a new drive using the command line commands (albeit it didn't recognise some of the syntax so I had to lose specifying the file system in the create primary partition line, and I had to lose the format and label properties when creating the EFI drive but otherwise it all worked). However, when it came to actually installing windows on the newly formatted primary partition, I got the error message from the Win 10 installer that it was a GPT partition. I have tried installing Windows 10 on the Samsung 960 Evo that I used to have Windows installed on (but inadvisably wiped lol) and now I just can't get it to work. I also tried my Samsung 850 Evo and that didn't work either. I tried either installing into unallocated space or a correctly created set of partitions created by the win installer itself, using either my licence key, or without a licence key, and none has worked. I tried using the install DVD as well as a USB installer (created by Microsoft's exe), and neither were successful. There doesn't seem to be any difference in performance between the DVD and USB, if I create a DVD from the genuine Windows 10 iso. When it comes to actually booting up the installer, I've tried with and without CSM Support enabled, no difference in the end failure to install Windows. It also seems the BIOS doesn't boot up the UEFI part of the installer DVD unless I set the installer at boot order no.1 in the BIOS, if I just select the DVD and save and exit it doesn't load it up. I can start the DVD from Clover but not the USB installer, that has to be done from the BIOS boot order. The only thing left to try I think is to give up on UEFI and try formatting a dedicated drive to MBR and trying to install Win 10 on that.
 

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@PliSsK
...I got the error message from the Win 10 installer that it was a GPT partition...
Make sure you boot the USB installer with the UEFI in the label of the USB drive when you select a boot device. This will allow installing UEFI mode on a GPT formatted drive.
 
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