My Lenovo G500s got problem with power on. When I push the power switch, I can see the webcam indicator light power on, and usually, it light up for a while, then light off, then CMOS loading/boot. But the problem is, webcam indicator LED light up, then nothing happens after that.
After some googling (thanks to Google), the problem is related to CMOS memory battery, means the CMOS need to reset. And also, you may need to change the CMOS battery. But for a while, you can open the laptop cover (unscrew it), then take off/out the battery, then reassemble back the cover, then now try power on your laptop.
Maybe at first the problem still the same, stuck at webcam indicator light on. Don't worry, try push the power button and hold until webcam indicator light off. Then release the button. Then push the button again to power on.
So the problem is related to CMOS memory, maybe somehow corrupt or, I don't know. I just know that the CMOS memory need to be reset. So the keyword is "CMOS reset" or "clear CMOS".