That sound is your power supply(it does that when it powers off too fast when powered on). About the frag,i am going to tell you something similar that happened to me. I once wanted to add a fan on the gpu haeatsink(the passive one,without the fan on it)to make it cooler. I did, but the dvd drive was pushing on it when closing the chassis and after some days i started having this issue(frag,but after some attempts it boots normally). I removed the fan and it was fine again. So my guess for both of us is a cracked solder join. When it is cold,there is no connection and with all these attemps,the solder gets warm(expanding in the proccess)and then it makes connection. My suggestion here it to do a full reflow off the motherboard from both sides and check if that fixes the problem. Have a nice day