I've had trouble booting my computer lately. The post gives a short beep. Then, the red DRAM led flashes for a second and the red cpu LED flashes for a second. From their, the computer boots, but after about 30 seconds, it shuts off. I also noticed that the 200mm fan on the top is not spinning and if I try to spin it manually, the computer shuts off. Does anyone know how I can fix this?