I was trying to upgrade Ubuntu from 16.04 to 16.10, but during the upgrade process an error popped up (it said something like 'there is an error in system files' but I don't remember exactly).
The upgrade window froze and I forced quit.
Now, after restart Ubuntu is stuck at purple screen. What should I do to reach the login screen? I have important files in my system and now I can't reach them also. I also have windows 8 installed pc and I can start windows normally, if that's any use.