Thanks for the update!
Yes, the boot configuration files should be stored in the reserved 100 MB partition. Solving this problem manually may not be easy, so I suggest booting from a Windows 10 installation media and executing several boot repair commands using the Command Prompt.
Click here to see the explanation:
Since you have Windows 10, you cannot boot into recovery just by pressing the F8 key while the computer is powering on, which was possible with Windows 7 and Windows 8 (Shift + F8). Instead, you need to boot from a bootable Windows 10 disc or a bootable Windows*****
In case you don't have any of those, you can create it easily. Here is how:
First, go to this link in order to download the Windows 10 media creation tool:
Run the tool and select the Create installation media for another PC option and click Next. You will then be able to choose between creating a bootable USB flash drive or a bootable disc (ISO file). My recommendation is to go with the bootable disc so that you can always have your own Windows 10 installation disc if needed in the future. So, choose the ISO file option and click Next. Select where to store the Windows 10 ISO file and let it download. It could take some time for it to finish.
When done, you will need to burn the ISO file onto a blank disc (DVD). To do that, you can use a free program named Free ISO Burner which you can download on this link:
Start Free ISO Burner and insert a blank DVD. Click Open and locate the ISO file you downloaded using the media creation tool and then click Burn. After you have burned the disc, restart the computer. It should then load the Windows 10 setup from the disc. If not, you will need to access the BIOS (UEFI) and set booting from the CD/DVD drive.
At the Windows Setup screen, you will then be given a way to (re)install Windows 10, or to repair it. Select "Repair your computer" option located in the bottom left corner. The "Choose an option" screen will appear. On that screen, click on "Troubleshoot", then click on "Advanced options" and then click "Command Prompt".
The computer will then start the Command Prompt. Once started, execute these 3 commands below:
Note that there is space after "bootrec". When done, you can eject the Windows 10 installation disc and restart the computer.
Hopefully, that will restore the correct boot configuration.