Rrrr you only mention having 2 drives at the end. Windows has its own bootloader and that came into play when you only had Windows as the only OS.
When you installed Mint , that will have installed grub as the bootloader and its picked up that there was another OS. Grub would be .. well let me show you whats in my OS bppt directory
[email protected]:/]$ tree -L 2 boot (07-27 21:22)
│ └── boot
│ ├── fonts
│ ├── grub.cfg
│ ├── grubenv
│ ├── locale
│ ├── themes
│ └── x86_64-efi
But thats not the whole story i reckon your PC motherboard has uefi firmware and so i think you have a EFI partition , which is part of the boot system.
When you installed centros that also i think also probably installed grub(never used it) and took precedence and added the other 2 OS to the menu.
if you install efibootmgr , from the command line you can launch it and look at the entries.
Some days i think i understand the boot process and other days i think i don't get it.
And of course it all changed from when the MBR was involved and now mostly using gpt .
the basics in the old days was that after the POST test , a small bit of code at the start of the 1st partition 512 bytes held enough information and pointed at the next place in the chain to get things going which was legacy grub.
you can boot Windows 10 and Linux on a uefi system using rEFInd on a usb stick. You can at the grub prompt hit the "e" key to get grub options. you can even get the grub command prompt then play with it to see what it can see etc . you can get to the grub prompt after htting the 'e" key by hitting F2 or Ctrl-C
When you see the prompt i.e grub >
you can type ls
it will basically output what it can see. From that prompt which you will get to when your system has a problem finding the grub files is to help it manually.
worth a read also http://rodsbooks.com/