[Fedora] Dual Booting Windows 10, Fedora 23 system broken (not UEFI)

I have a Dual booting Windows 10 & fedora 23 system which had been working fine until I screwed up the boot process when I let Boot-Repair on a booted Ubuntu exteal drive run on the system (it was 32-bit Ubuntu if that matters).
(I was tinkering with a 32-bit Ubuntu exteal USB drive to boot another older computer from...)

I have tried a BUNCH of things to fix this including ruing Boot-Repair, tinkering with the activation and boot sector designations in GParted, but still no joy... Right now I do have it working to boot into Windows 10, but no Grub menu comes up to give me an option to start fedora instead.
When I try to run Boot-Repair (from a thumb drive), I get:

"Please enable a repository containing the [grub2] packages in the software sources of Fedora release 23 (Twenty (mapper/fedora-root). Then try again."

How am I going to do that if I can't get fedora 23 to boot in the first place?

I do have a pastebin from Boot-Repair that I can share if anybody is interested and knowledgeable: Analysis of HP dc5800

I don't want to "tinker" with any more of the various incantations I see here and there for fear of making things worse since I really don't understand the whole "active partition, boot, grub" system/process in the first place.

Is there a good online reference to get a "bird's eye view" of how all of the boot pieces fit together?

"active partition, boot, grub, OSes ..."

Thanks in advance for any help or guidance.