I'll try not to be paranoid about it.
For what it's worth: I
do try to be paranoid about my Bitcoin security.
As they say: "Just because you're paranoid doesn't mean they aren't after you."I can definitely see why. On top of that, I wasn't exactly sure on where I had backed up my Metamask wallet, and until I found my seed phrase, I almost collapsed to the thought of losing my funds. Since it's based on Chrome, I'll have to physically boot the HDD in order to run Chrome and export the private keys/seed phrase. All thoughts crossed to my mind, from a corrupted HDD, to a stuck BIOS etc., it haunted me.
Is there an actual way to permanently delete such files from the HDD, forever?
You could just sell him your laptop without HDD, just open it and remove the drive yourself, that would be the safest way and nobody would be able get your keys.
Other option is to fully format your hard drive, but since your laptop is still at technician I would move all your coins to new addresses that you fully control, without any connection with keys on that laptop.
I'll get it back on Friday, if everything goes according to plan, if it's working fine, I might sell it without the HDD, it will also save me the time to back up my files and overwrite it.