Yes, indeed trust him!
There are several methods people thinks are safe for getting rid of data.
FDISK is a disk partitioning tool, the only part of the Disk FDISK affects is the partition table, using Fdisk will only tell a computer that there is no partition, all data will be left intact.
2nd Format. (high level / quick format)
The only thing a quick format does is erase the first bit of each block on the disk.
o roove y oint, 'm ure ou an uess hat his s eant o ay
(to proove my point I'm sure you can guess what this is meant to say)
3rd Format (low level / disk zero)
All the bits on the disk are reset to a set value. (zero) and all data on the disk is lost...
the disk is made up of magnetic particles, each particle sits in a particular domain, (the way it is facing eithe 1 or 0), you'll know that if you leave a screw driver next to a magnet for a long time then the screw driver becomes magnetic...
the same thing happens with the disk, the disk surface begins to adhere to the domain on the data layers, thus when a disk is low level formatted sometimes the bits can start to re-align them selves back totheir old domains,
to get around this there is the standard 5 swipe zero, all the bits are written to 1, then all the bits are written to 0, 5 five times.
This is pretty secure and helps to eliminate the residual magnetism on the disk surface.
However it is suggested tat with the aid of an electron microscope a lab team may still be able to view data that was on the disk, by ananlysing the residule traces of magnetism.
The only to truly destroy a disk is to grind the disk surface into a fine sand.
for most home and business use a 5 swipe zero will be enough though!