text: If it is a Windows system, what is happening is the system is going into hibernation when you close the lid.  Hibernation causes all the internal electronics, including the display drivers to shut down as an energy and power savings technique.  You can change this by going into the control panel and selecting Display.  Somewhere in this folder are the options that allow you to select what you want the system to do under what conditions, such as lowering the display.  If you need help, select Help on the menu bar and search for display power settings.