booting da win

[stan]

Update on my experiment. I am extremely familiar with installing Linux, and as I said above, the external SSD I configured with Mint was set with MSDOS partition table, which it is. But I also explicitly told Mint (using "something else") to install the GRUB bootloader on this external SSD... but it did not. GRUB was installed into the /boot/efi partition on the Windows internal SSD instead. This is why I get the grub> prompt when booting with the external SSD removed.

If these drives were both internal, this would be fine. I could choose the Mint drive to be first in the boot order, and GRUB would allow either OS to be booted... the outcome desired by the OP. I don't want to have the external always plugged in, so the Windows Boot Manager is set to boot first again, and I have to use the Boot Menu to select Mint if I want it instead.

It seems that Mint decided it knew better than me how to install itself, although I don't necessarily agree with that. This external drive will not boot on another computer now because it has no bootloader, except on my Windows laptop. This explains at least one reason why the OP's original advice to disconnect the Windows drive before installing Linux to a separate drive is a good idea. However, it is probably also true that Mint only boots at all because it created a UEFI bootloader... otherwise, I would have needed to change my BIOS settings to Legacy, or both UEFI/Legacy if that option is available.

I sometimes wonder if anyone truly understands the whole UEFI/BIOS/GPT/MSDOS/ CPM/LEGACY blah. What a mess.

I agree! And it sure isn't me!

 

[KGIII]

Did try. No luck.

I'm gonna leave you in the hands of the others. The boot-repair was my only option/fix. Others here are MUCH more adept than I am at multi-booting.

 

[old_man_and_the_linux]

Hi guys and the fishes,
Last few days was trying all suggestions. Best I could get was the proper grub screen for dual boot: ONLY if I selected my windows drive after F12. That told me that grub was installed in C:MBR but was unavailable in normal booting. I intuited that if I could get my drive C to the state it was before I installed Linux, I may do a fresh install of linux and get the GRUB to work properly. (Forgive this prattling of the innocent).
Well, for 2 days I tried to get back Windows boot manager on my C drive. Nothing worked. GRUB ruled.
Incidentally, My C drive is SSD. My BIOS is Dual UEFI/Legacy. I was using Win 7.
Then I wondered that perhaps if I upgrade to Win 10, the boot loader etc would get overwritten and GRUB would get replaced.
I did. GRUB did not get overwritten on installation process of WIN 10.
However, after installation (WIN-10) was complete, the GRUB started working as it should.
Conclusion: Mint 20/ 20.1 is compatible with Win-10 but not with Win-7.
Make any sense?
Should a Win 7 user stick to editions 18 and earlier of Mint?
What do all of you Gurus think?

 

[stan]

Conclusion: Mint 20/ 20.1 is compatible with Win-10 but not with Win-7.
Make any sense?

In your case, but it may not be true for others. Glad you got it working!

Should a Win 7 user stick to editions 18 and earlier of Mint?

Not in my opinion. Win 7 has reached EOL and should be retired. But it was a popular OS and it's hard for folks to let go. Linux Mint 18 reaches EOL in just 3 more months (April). Maximizing the life of old hardware is great.... using out-of-date operating systems is not-so-great.