I have occasionally performed a repair install when things weren't right, but I've also booted up with it and selected Repair your computer on the Install screen and performed a couple of cmds when the machine wouldn't boot or was hanging on boot.
Those cmds are -
bcdedit |find "osdevice"
For clarity that is a Pipe symbol before find and is the uppercase of \
Then using your partition letter instead of the x I have exampled, enter -
dism /image:x:\ /cleanup-image /restorehealth
Then again using your partition letter instead of the X I have exampled, enter -
sfc /scannow /offbootdir=X:\ /offwindir=X:\Windows
Note the space before each /
Enter exit to close the cmd window and restart.
