Took it to a technician who claims that it's power unit or something is broken and it's not receiving power.
Depending on the laptop this could be a cheap part to replace.
While I wouldn't really bother about the rest of my files, I'd rather not have someone recovering my wallets this way.
How about passwords? Creating a new wallet and moving all your coins is quite easy, but your browser might have access to many accounts.
Is there an actual way to permanently delete such files from the HDD, forever?
There's a software
shred and there's the hardware
shredder.
I would prefer not to trust anyone with my data, so I would have removed the drive before sending the laptop to a repair guy.