/P:count Zero every sector on the volume. After that, the volume
will be overwritten "count" times using a different
random number each time. If "count" is zero, no additional
overwrites are made after zeroing every sector. This switch
is ignored when /Q is specified.
if you want to do it properly it will take a while
the one I use is dban https://sourceforge.net/projects/dban/
make sure you select the correct drive tho
out of interest what are u all doing with old HDDs?
This is the best choice if you can already hear the sirens.magnet works really fast or a hammer