I see that you are having reboot problems on your system after you plugged in a microphone in one of the analog jacks.
I recommend testing the system out of the chassis on top of a non-conductive surface; this could be a wooden table or a newspaper. Also while you are taking the motherboard out of the chassis, you can clear the cmos by removing the power cables from the motherboard ( 2x12 and 2x2) and the cmos battery for an hour. Once you have the motherboard out of the chassis and cleared the cmos, we need to test the motherboard on a basic configuration, this means have the system as basic as we can. Have only the power supply and the processor with its Heat Sink. We won't need memory or any other device as we are seeking for 3 long beep tones. If you receive the beep tones, then turn off the computer and test with one memory stick and the monitor connected.
Please note that you should not have connected any front panel audio or USB.
If the problem continues, you should try to replace the motherboard.