Why won't my laptop turn on?

Just to be clear, this is my brother's laptop. Firstly, he has moments where he's accidentally dropped it or slammed it (needless to say he doesn't know how to take care of his stuff). Secondly, he's always torrenting stuff (and we don't have any kind of protection). Third, the laptops are used and have beeb refurbished. And finally, the laptop's charger port is loose.

I've tried to exchange laptop batteries from mine to his; the light doesn't even blink. I've tried to disassemble it, check the charger port, reassemble it (thought not very well, I'm still a newbie); again it doesn't even blink a small light. Nothing. I don't know why it doesn't turn on and I would appreciate if anyone could help me out. Thanks.