The Topic header is fairly much of the question, and will add a bit of extra details.
My main PC will be running Windows only, as I have a slew of computers well capable of running the latest Linux Mint (currently 18.1) on. After I built it, and before I built the 2nd, then 3rd, not to mention a couple of others, plus two notebooks with the OS, have decided to keep my best computer with a single OS, and that's Windows 10 for the time being. May later perform a system image & revert back to 8.1 Pro w/Media Center, though that's not cast into stone yet, or may never happen, as it would cost me point in some benchmarks, of which some penalizes one w/out the latest OS installed.
So in the UEFI, there's two entries, Ubuntu & Windows Boot Manager, which I presume came from the small partition where one places the Linux bootloader, as the OS is no longer on the system. However after exploring the partition with MiniTool Partition Wizard, there's Grub entries in there. Can I assign a letter to the partition temporarily to delete those, revert back & reboot, praying that all will be OK & Ubuntu will no longer show in the UEFI setup (cannot delete it there, can only move up or down) & all will be cleared afterwards?
Or will more drastic actions be needed? I don't see the need for reinstall to purge a few entries, nor do I see the need to revert to a near year old backup image prior to the dual boot setup, only to have to perform updates/upgrades to most everything on the OS. To include installed software, which by now are many versions behind. If I were reverting back to Windows 8.1, this would be a non-issue, could accept updating, it's simply not in the plans for now.
Since there's no physical Linux Mint now installed, the only other specs I have is the first in my sig, which is copy/pasted below.
And since it was Linux Mint 18 Cinnamon which did the damage, I feel that it should be addressed here, if a Moderator feels different, can always feel free to move where it needs to be.
Am hopeful this will also clear the Ubuntu entry in the UEFI w/out resorting to resetting it, which would cause me to lose custom changes, in particular, all the time & effort required to set the CPU multiplier to jack up the CPU rate (all cores) to 4.2GHz. Prior to that, these were more variable & never could get all cores to hold the same multiplier, which dictates the CPU power scheme. So if at all possible, a UEFI reset is the last thing I'd want to do.
Thanks to all for any solution offered to address the situation.