If you do not want to troubleshoot the crash and only want to backup important files this can be accomplished using a GUI:
On a working computer create:
a bootable Ubuntu flash drive:
Create a bootable USB stick on Windows | Ubuntu tutorials
https://tutorials.ubuntu.com/tutorial/tutorial-create-a-usb-stick-on-windows#0
https://www.pcworld.com/article/2147063/linux-to-the-rescue-how-ubuntu-can-help-a-computer-in-distress.html