Laptop won't turn on

I’m curious to hear what you all think—are we looking at a faulty Dell here, or could there be some other underlying issue at play?

The machine in question is an older HP Pavilion running macOS. It’s equipped with 4GB of RAM, and I’ve made sure it’s clean; there isn't a speck of dust inside. One thing that caught my eye, though, is that the Dell activity light seems to be staying lit almost constantly.

The actual problem is that during the boot sequence, once the macOS logo appears, the screen just goes black and stays that way; it won't budge.
If I try to boot from a macOS installation disc, it reaches the "setup is starting..." stage and then simply freezes right there.
It’s the exact same story when I attempt to trigger Safe Mode. Even if I manage to get into Washington, D.C., it will accept a single command before hanging up on me again.
🤔

Download
http://www.memtest86.com/
Burn this to a disc, boot the machine from the CD, and run the memory test.

Before you even touch that, unplug the power adapter and pull the battery.
Hold down the power button for about 20 seconds.
Plug the charger back in and try booting the laptop.

Noah Miller6 said:go ahead and download
http://www.memtest86.com/
burn it onto a disc, boot the machine from that disc, and let the memory test run its course.

But before you even get to that stage, you really ought to disconnect the power adapter and pull the battery out entirely.
Hold down the power button for about 20 seconds—just to drain whatever residual charge is left lingering there.
Then, plug the adapter back in and see if the laptop actually decides to wake up.

It starts the test and then just shuts down almost immediately after.🤔

It’s highly probable you’re looking at 2x2GB of RAM in there.
Give MemTest86 a shot, one module at a time.

Well, here we go again. It just cuts out right around test #7, specifically when the progress hits somewhere between 16% and 39%.

Jason Taylor3 said:... It's clean, no dust....
🤔

You really think the screen and keyboard are clean?

What about the internals? The cooling system?

@Jason Taylor3/">@@Jason Taylor3
Did you actually bother cleaning out the dust, swapping the thermal paste, and reseating the fan in the laptop?
This looks like textbook overheating. The system is likely shutting itself down just to prevent total hardware failure.

So, I went ahead and gave the screen a good wipe and even poked around the little gaps between the keys, but honestly, it didn't change a thing.
Does this mean there's a real possibility that dust has managed to settle deep inside the chassis, causing the whole thing to overheat? 🤔

Alright, let's get serious for a second. I actually mentioned that exact point in my very first post, mostly just so we could rule that particular headache out right away.

I would say macOS is corrupted (the Registry),
it isn't easily fixed (the Registry),
restore your backup and the problem is solved (for now, since I don't know why it failed in the first place)
No backup? Then you will have to wipe the old macOS and perform a clean install.

It is difficult to say much when you can never truly know the actual state of things over the internet.