Why does my laptop make a constant bell ringing sound? (Not a beep but an actual bell like a church bell that rings every 2 seconds w/ a periodic whooshing sound like a plane going by - not making this stuff up.) How do I make it stop?! It even rings over other audio! I rebooted the laptop, which made the sound go away for awhile, but now it's back! And it's not the sound of the laptop's fan. This started 2 days ago... please help!