At this point, perhaps the best option is to seek professional help. In this case, preventative measures may already be too late. It's the culmination of a gradual process where more and more hours are spent in front of the screen and fewer hours doing other things: housework, studying or doing homework, meeting up with friends, playing sports, learning to play an instrument, etc. Therefore, it's not that hours and hours are spent on the computer suddenly appear overnight, but rather that computer use has likely increased little by little, progressing from use to overuse and, perhaps, addiction.