Ubuntu version 1.99 will not boot up after randomly shutting down.

I have Ubuntu version 1.99. I have had this computer for months with the OS already installed and has worked fine for me until one day it decided to shut down randomly and ever since, I have not been able to get it to boot. I don't know why this is happening.

    I am also a beginner to Ubuntu. I usually just click on the top line on the purple screen of options: Ubuntu, with Linux 3.8.0-38-generic and it brings me to my home screen but now when I click on it, it brings me to a black screen with an underscore flashing. I have also tried the recovery mode option and I have typed in a few suggested built-in commands and also suggested commands from other ubuntu users and still get nothing. I feel like I have done everything I am capable of and I am in desperate need of help.