There is no way to completely erase files without specialist utilities and experience. ...
I think Red meant without using the lump hammer there.
That isn't true. There are plenty of easy to use software's that you can run via desktop or at boot to erase a disk well beyond recovery and no experience is needed. It's simply ...
The easy to use software probably won't work. Modern ('SMART' capable) disc drives are capable of transparently remapping into use, on-the-fly, unused spare tracks which are available on the platter(s) to replace tracks which become unreliable as the disc wears.
When the disc firmware considers information stored long term in the dodgy tracks might be unsafe then it remaps the dodgy tracks, and it even keeps a running tally of what it's done which you can see using S.M.A.R.T. software.
But the information on the dodgy tracks is still there, and still readable. These tracks will never be addressed by your off-the-shelf disc erase package but are easy meat for even an average disc drive hacker, or the FBI.
The only way to get rid of data is with a lump hammer
That's correct. There is no really reliable way to completely erase files without destroying the drive.
That would be my preferred option if, let's say, there might be something on the drive that could put me in prison.
Even if you use DoD approved over-writing software and no tracks have been remapped by the disc firmware, the mechanical tolerances on drives leave enough residual magnetic field from erased data that it can often be recovered.
But we're talking atomic force microscopes and megabucks, not Norton Undelete from Amazon. So you need to do a sort of cost-benefit analysis.