I'm new to this forum so be nice. I have a ASUS A7N8X board with a Allied AL-A400ATX power supply. Starting this weekend, with no notice, my system will not boot up. Instead, it seems to be stuck in a On/Off loop. I can't get into bios, safe mode or use my bootup floppy because the cycle doesn't last long enough to reach that part of the startup routine. The front On/Off switch does not work. I have to power down by using the main power switch on the Power Supply. I think I've narrowed it down to my power supply or my motherboard. I tried a new hard drive . . . no change. After disconnecting all my various drives including hard drive(2), CD, DVD, and Floppy; I am still getting the On/Off loop. The power supply seems to be automatically turning itself on/off. Even when I disconnected the On/Off switch cable from the motherboard it continues. I looked at the capacitors on my motherboard and there appears to be no sign of bulging or discharge. Do you think I should try to replace my power supply? or motherboard? or something else? I'm getting in a little over my head, but don't think I'm ready to buy a whole new system. Please advise.