I run a computer repair business and I received a Compaq C series laptop that doesn't boot on power up. I took a video sample of the problem.
It just stays like that, in fact, I've left it on for 30 min.
After spending hours trying to go through the elimination process (RAM, GPU, Fans, etc), I removed the battery and tried running on AC power only, and it worked. It booted fine and I got into the OS. I didn't know that the battery could stop a computer from booting. I guess you do learn new things every day.