Hi LANDCRUISER. Are you saying that the longer you leave the computer off the longer the monitor stays on, or the longer you leave the monitor off, the longer it will stay on after restarting? When the Mitsubishi isn't getting a signal it goes into standby mode, so if the computer is overheating and shuts down, the monitor will not be getting a signal and as I said above it will go into standby mode. The first thing I suggest you try is opening the computer case and clean the fan blades and heatsinks of all the fans (CPU, graphics, chipset and case fans - you may not have all those but you will definitely have a CPU fan). The PSU also has a fan, and although that often gives this problem it is not recommended that the inexperienced open the box to clean it because of the high voltages in there.