MacBook Pro won't turn on. How to fix?

Question

macbook

Hello. The MacBook Pro 2006 stopped turning on.
I understand that it's a mammoth, but it fuses with documents and the browser with a bang.
Worked properly on Windows 10, since MAC OS is old.
When turned on, even an apple does not light up, but if you hold down ALT, it suggests where to load the OS.
I understand that everything is fine with the display. Tried resets, took out the battery. What else can be done and where to dig further?