Bug or unstable work of system

I'm new in linuxcnc and today have made my first rough processing on detail.
When the process was finished, I chose MDI and write to "G1 Y28" to move to this point and pressed enter. But instead of moving axis I saw black screen










In this window I can't do anything and restarted computer. But it not loads linux anymore. I saw such screens after each restart and turn off the supply:


What it should be? I want to renew installation but it will be later.
I installed latest release 2.7.4.
I suspect that GRUB damage.

hard drive failure?

Really I don't know what happens.

First image writes what is wrong.
Currently I will today reinstall linux try one more.

I have reinstalled linuxCNC and tried everything that I have made before crash. Every thing is OK. It possibly could be hardware crash because computer is very old.