I've used recovery software on many Hard Disk Drives. Provided that the hardware and electronics are working and provided that the data hasn't been overwritten by saving something in its place, then recovery is simple.
The military have equipment that can often recover data even if it's been overwritten!
To truly render something unretrievable you pretty much need to wipe the drive like with a cloth or something. Then smash it with a hammer.
Or else an IT nerd with enough time and patience can find it.
I've used recovery software on many Hard Disk Drives. Provided that the hardware and electronics are working and provided that the data hasn't been overwritten by saving something in its place, then recovery is simple.
The military have equipment that can often recover data even if it's been overwritten!