ASUS G50V startup problem

I've had this laptop for about 4 years and today for the first time after trying to start the computer, it failed to boot and there was a continuous high-pitched noise. I tried turning it off and on a few times, same problem. I then removed the battery and it started up fine. So now I'm using the laptop without the battery and am kind of nervous about what to do next.

One additional point - a dumb one I think - a couple of times after I bought the laptop, I caused it to crash by accidentally putting an audio jack into the wrong input (e.g., a USB port). I read on forums to take out the battery, stick a pin in the reset hole, and it will start up again. I was going to try that with the current problem, but - this is weird - I can't locate the reset hole.

 

Forget the second part of my question - I found the pinhole.

 

Found this for the noise problem.

 

Thanks, but I don't see how that's relevant to the problem I experienced, which occurred when I tried to turn on the laptop. In fact, my headphone jack doesn't work anymore and I've long since replaced it with an external USB audio device. Strange, but everything is back to normal, booting up OK with the battery reinstalled. Still, it was pretty scary turning on the laptop and getting nothing but that squealling noise. Can't be a good sign.