Why won't my laptop turn on anymore?

It’s either your battery being completely dead (although laptops run even when batteries are removed), or since your laptop is so old, it could be a power supply issue, perhaps the pin inside the charge plug, or the cord is bad, or something like that.
I’d start looking for a new laptop; they only last about 5 years max (except intel thinkpads, which are like dinosaurs: durable and old)

this is actually a common issue with laptops that are older / have bad battery.Take the battery out and with it plugged in try turning it on. That will tell us if its an issue the battery and if so then you can probably replace the battery but there could also be another problem with the internal power supply.

(Thinkpads are made by Lenovo, and previously by IBM who sold the brand to Lenovo. They do have Intel processors in them. And, yes, they do last a long time.)

Without getting too technical, if the battery is bad enough, leaving it in actually sucks power away and is actually worse than no battery. It may even lead to permanent damage in other systems.

Now you know why ignoring warnings is a bad thing.

@dabbler My Powerbook 180 is still going :D

Yeah, I left in the battery charged cuz that’s the only way my laptop would turn on lol. My warranty expired long ago. I’m having a friend look at it, I hope he finds out what’s the issue. I can’t afford a new laptop. Seems like I need an upgrade on all my things: car, phone, laptop, camera.

A typical Lithium-ion battery like that in most laptops, phones, MP3 players, etcetera will lose at least 60% of it’s capacity in four years assuming normal use. If you do things like store it fully charged, it dies quicker; you can kill the battery in under three years, and you will definitely notice a drop in longevity by two years. Exposure to high temperatures (like inside a closed car in the summer) can reduce the battery’s lifespan to mere months.

The general rule of thumb is to plan on a Lithium battery lasting two years.