You should continue with "diskpart.exe" commands:
select disk 0 - this makes boot disk selected.
list volume - gives a list of volumes, their sizes, drive letters, and most important which is the "System" volume !
If "System" volume (say it's Volume number 3) does not have a drive letter use following commands:
a) select volume 3
b) assign
Now examine again volumes with "list volumes" - you will see there is a drive letter assigned to "System" volume. Let it be drive letter K:
Now type "exit" to leave diskpart.
At command prompt type:
K:(enter) - this will make K: drive current.
Now you can use "dir" command to examine files, "cd" for changing directory, "dir /ahs" to display hidden system files and command "del file_name" to delete a file.
I suggest if you do not have much experience with system(boot) files to format partition(volume) K: Then you can run "StartUp Repair" which will recreate necessary boot files on "System" volume.
format K: /q - q is for quick format.
You should run "StartUp Repair" up to three consecutive times with rebooting after each run for best result (one run of StartUp Repair is not always solving boot issues!).