if anything on PC you want to save, try this: http://www.howtogeek.com/howto/windows-vista/use-ubuntu-live-cd-to-backup-files-from-your-dead-windows-computer/
If you need a win 10 installer, download the
Windows 10 media creation tool and use it to make a win 10 installer on USB
did you try to reinstall Win 10 and use a win 7/8 licence to activate? You don't need it anymore, since win 10 been on PC already, when you reach screen asking for licence key, just click "I don't have a key" and win 10 should activate itself on install