I'd start with a blank drive. In your first photo I can't see it all so I'm going with:
1. Boot GPARTED or any Linux to run GPARTED and remove all partitions.
2. Install W10 to said drive. YOU SHALL NOT CREATE ANY PARTITIONS OR FORMAT BEFORE THE INSTALL OF WINDOWS OR YOU WILL FAIL.
Let W10 do all the partition and formatting.
If the GPARTED doesn't clear the drive, use DBAN.
If DBAN doesn't clear the drive, pull the drive and DBAN it on another computer.
This is not a Legacy BIOS issue.
I am trying to clean install Win 10 on Acer V5-751 but whenever I come to 'Windows Setup' Drive allocation - format, delete, new section it says 'Windows can't be installed on this drive - The selected disk has an MBR partition table. On EFI systems, Windows can only be installed to GPT disks'.
I figured it was due to BIOS being in UEFI mode, so I have tried to change it to Legacy and disable 'Secure Boot' like on other laptops/bios. But unfortunately, I cannot find UEFI/Legacy Boot menu or Secure Boot disable/enable options on Boot tab of this specific Acer laptop. But only see Boot priority order sub-menu.
So I googled, youtubed everything I enable that option. Most suggestions say I have to set a Supervisor password on Security tab which I did and hit F10 to save and restart back to BIOS and it would show. But it didn't Also I have already enabled F12 Boot menu option in Main tab. Also I have used Rufus to create both GPT and MBR bootable usb flash win 10 but both doesnt work. Thus I have no idea how to install Windows 10. Please see attached photos and advice me how to make this work. Thank you, much appreciated.
https://imgur.com/a/DhUBm3x

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