On another PC download this:
windows 10 media creation tool Use it to create a Win 10 installer on USB or DVD
You should also look at this: http://www.howtogeek.com/howto/windows-vista/use-ubuntu-live-cd-to-backup-files-from-your-dead-windows-computer/ if you want to save anything off PC
Now, once you have an installer and have copied anything off PC you want to keep, I would suggest a clean install. Your current install is broken. this is best fix
Change bios boot order so USB or DVD are 1st, hdd second
boot from installer
follow this:
http://www.tenforums.com/tutorials/1950-windows-10-clean-install.html
When you get to screen asking for licence key, click "I don't have one" and Windows 10 should auto activate itself on install.