(SCARY) Why my computer screen kept blinking on and off after i put in the movie called the "DEVIL"?

i decided to put in a movie called "DEVIL" and soon i put the movie in and my computer screen started blinking on and off and it was around 3:00 A.M. Everyone was sleep but me and after i saw the computer screen blink then i heard some noise in the kitchen and then that's when i turn the movie off. Sometimes if i wake up in the middle of the night and it sound like someone walking up the stairs.