Copying the bootmgr from the 100MB active partition or the recovery partition to C:\ is extremely simple with EasyBCD. You can download EasyBCD from this website
(click on "See Plans" for free version).
The bootmgr will not be moved from the original location - it will only be copied to the C:\ partition. The C:\ partition will be activated and the 100MB partition will be deactivated.
NOTE: The free version download of EasyBCD is at the bottom under "Download free for limited, non-commercial use". Registration is not required to download.