Erasing a hard disk easily

[amilabs <amilabs () optonline net>]

I have a bunch of old computers I would like to donate. Old laptops with win
95/98 on them and some old tower desktops all circa 1995-2k. 
I would like to know if I can just use a magnet to completely wipe out the
data for obvious security reasons. I have heard about the disk erasers like
active kill and Perl utilities for this but with the ability of data
ghosting etc. is this enough? Can I use a big magnet like a speaker magnet
or something like a degasser to just wipe out the data without having to
boot these old boxes and go through all the extra work.

Thanks 

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