One trick is sometimes the ram gets into a weird state. Take it off power, disconnect the battery, and then remove the ram. Hit the power button a few times to clear the caps. Put the ram back in and reconnect power. Half the time it should boot right back up after this.

If that does work then it’s probably hardware. Take out the ram, and then attempt to boot it without the ram. When you boot it should scream at you (because there is no ram) by beeping a lot. If it doesn’t, the motherboard is toast. If it does that is good because the mobo is initializing at least, but at least one of the sticks of ram is probably toast. Run memtest with different combinations of the sticks to determine which one(s) are toast.

If you can, I recommend removing other devices from the board while testing, mainly your drive.