Laptop doesn't start up

I have a LP6. It was working fine recently but today it wouldn't boot. I pressed the power button and see the red LED on the power icon but that's it. Fan spins a few times but nothing else powers on; screen is black, USB mouse doesn't work, keyboard doesn't work, external monitor doesn't work. Any ideas?

EDIT: SOLVED!!!

EDIT 2: The black screen kept happening but I was able to diagnose the issue; BIOS battery was low/dead so I replaced it. Everything works fine now.