I got my laptop back out since I haven't been able to use it for a year and a half. When I plugged it in, the fan and the power light comes on. So I was thinking, that doesn't sound like a battery problem. I wrote my problem online and found on a website that someone else posted they had the same problem, black screen but fan and lights work.
One poster wrote before turning on the power, open the lid as far as you can, which I did, then turn on the power. Guess what, my computer now works, and looking at the replies about 10 other people fixed their computer the same way. So it's not a battery, it's probably not even a software problem, some kind of hardware problem.
Hp pavilion has black screen problem [Solved]