Question Re installing Windows on Ubuntu-Windows 2 drive dual boot system


Oct 18, 2015
I really need some help getting my dual boot Ubuntu - Windows 10 setup working properly.

The issue is a partially corrupted Windows install do to a recent aborted format operation.

I originally partitioned and set up my dual boot over 2 years ago and didn't keep detailed notes.

I can boot into Ubuntu without issue. I normally switch between the 2 OS's by booting into UEFI and selecting the correct drive.

So 2 separate physical drives.

A Samsung 850 EVO 1TB drive is my primary boot drive (Drive 0) that I have partitioned for Ubuntu as follows.

    dev/sdb1    esp    fat32    10MiB

    dev/sdb2    root    ext4    40GiB

    dev/sdb3    home    ext4    650 GiB

    dev/sdb4    swap    linuxswap    128GiB

    unallocated                                 123 GiB

The drive which should contain my Windows install is a Samsung 950 PRO 512 GB nvme (Drive 1 in the attached image)

I have created a Windows 10 install USB and launched into it.
The problem I am having is that when I select either of the primary partitions on Drive 1 the installer says that it cannot install because of the GPT partitioning scheme on that drive.
I am confused. What do I have to do to reinstall Windows in that drive ?



Jun 16, 2018
Now, it says it can't install because you have a GPT, right? This means either the whole system is set on MBR, or you simply booted the install drive as such.

Check if any setting named "CSM Support", "BIOS Mode", "Legacy Boot" etc. is on your UEFI.
If any setting named BIOS, CSM or Legacy is on, you're running MBR/BIOS. You will need to make a choice, either format the Ubuntu drive as GPT, then turn the setting off, or format the Windows drive as MBR and keep it on.

If it's off, you're already running GPT/UEFI, so the USB is in the wrong mode. Use the boot menu of your BIOS to manually boot the drive up. It should have a "EFI" tag before the brand and model. If not, make the USB again using the Media Creation Tool.

Also, you'll need to configure GRUB after installing Windows as it will straight up ignore Ubuntu after it's installed.