carpo1, when anything takes this amount of time to happen I always suspect the problem to be heat related. Use the hardware monitor to check the temperature of your processor. You may have to run Flightsim for just under the time you normally get before a crash to see if that causes the temperature to rise significantly. Is your power supply capable of running the 1G Duron and Matrox G400, and is the graphics card properly cooled? You could try running your computer with the cover off and see if you get longer working time that way. If that helps, then perhaps a case fan will cure the problem.