So a laptop of a friend won't boot. I decided to try and fix it. One of the ways was to back up all the important files and reinstall Windows but the hard drive is so slow and keeps on disconnecting (it is connected via an external hard drive enclosure). So I searched for other ways and I saw the use of SFC scannow. I would like to try it, however I don't know if it will work if the version of Windows 10 differ. My PC is updated, while the laptop isn't.