Stuck while trying to uninstall lubuntu from windows 10 dual boot without windows installation media

shreehar

Please Help me ASAP,..i was using my friend's win10 laptop with lubuntu installed as dual boot for a week and have to return it now since i got my own latop(going to install Arch Linux Soon)
So i decided to uninstall lubuntu OS from my friend's laptop,..
i searched guides/tutorials for uninstalling without using a win10 installation media and found this video https://youtu.be/zl1Q2UiXu60
I was following everything said in that video until the bootrec /fixboot command,..for which i got "access is denied"
what happens now if i restarts the computer??
I don't know what to do know,..Please help me out