Yesterday I was working away at it when suddenly the screen freaked out, there was blocks of color everywhere and the mouse was acting strange (jerky, up was down, down was up etc etc) I had to hold down power to repair it. When it started loading it froze the little circle in the middle stopped spinning and I had to restart it. then the same thing happened again froze. So I started it in safe mode then restarted again. This time everything was back to normal . But today again I was just using the computer when everything went all glitchy again and same thing, this time when I went in safe mode the screen darkened and a box in the middle said something was wrong and to restart my computer. What's happening what could be causing this and what do I do!