How to fix - "“GPT detected. Please create a BIOS-Boot partition” while using boot-repair"

I had Windows 8 and Ubuntu 14 on my Dell XPS. I tried deleting Windows from Ubuntu by using this: https://help.ubuntu.com/community/OS-Uninstaller

I re-started my machine and saw a message which said No OS was found. I created a bootable USB having Linux Mint. When I plugged in the USB, at some point, I saw the grub error: "minimal BASH like line editing is supported". Online suggestions told me to do a boot-repair. On pressing F12, the USB wasn't showing in the UEFI mode, but only in the legacy mode. USB only in legacy mode

Question 1: How to fix this (if it is important to install linux in UEFI mode)?

Anyways, I reboot from the USB containing Mint in the legacy mode. In mint terminal, I try to run boot-repair: How to install the Boot-Repair tool in an Ubuntu live disc?

After following the steps, I get a Boot Repair message: "GPT detected. Please create a BIOS boot partition.(>1MB, unformatted filesystem bios_grub flag). This can be performed via tools such as Gparted. Then tryagain, Alternatively you can retry after activating the [Separate/boot/efi partition:] option" GPT error

Question 2: "Do I need to do this boot repair step in order? If I need to do the boot repair, how do I fix the GPT detected error?"

I noticed that my Ubuntu is still available somewhere, because when I tried installing Mint, I saw this message which detected my Ubuntu 14. Ubuntu detected

My objective is:

1) To keep Ubuntu as the only OS

2) if (1) is not possible, keep the new mint OS only. I can live with the data lost with Ubuntu.

In the windows world and by default on linux, there are only two possibilities:

old: BIOS-MB + MBR-disk
new: EFI-MB + gpt-disk

However if you have an old motherboard and a new disk linux gives you a chance

You can use a gpt disk with a bios-MB The key thing there is that you need to create a BBP — a tiny 1MB special bios boot partition near the beginning of the disk. [Not to be confused by EFI partition or linux separate boot ]

You can do that with parted though I'd recommend gpt things to be done with gdisk.

If you prefer (g)parted, do the actual partitioning with gdisk and examination/mkfs etc with (g)parted. This keeps alignment well. Thereafter marking the type as BBP may be easier with (g)parted.

This is a cutpaste of this post.

(No rep for making a comment. Mods can do that if they choose)