Not sure on where to post this, I apologize in advance if this isn't the correct section.

My laptop broke down this morning, taking my Bitcoin and Metamask wallet with it. Fortunately, I had both backed up so no losses there. Took it to a technician who claims that it's power unit or something is broken and it's not receiving power.

Anyway, back to the subject now, he's interested in purchasing it in case I do not want repair it, which is something I'm considering. However, my wallets are inside that laptop, someone who specializes in computers could potentially recover deleted files from the HDD.

I'm not sure if he wants to resell the laptop or he wants it for himself, my main concern though is that there's a way to recover deleted data. While I wouldn't really bother about the rest of my files, I'd rather not have someone recovering my wallets this way.

Is there an actual way to permanently delete such files from the HDD, forever?