>When you retire a disk from a project:

>3. physically destroy the disk so that the platters are
>   in as many pieces as possible. (sledgehammer, C4, etc...)

Multics used to have a purge command (I think), that would let you 
overwrite a file N times with various patterns.  However the advice
given to any multics customers asking how to recycle a disk containing
"sensitive" data, was to use a forge.  If the bad guys could spin the disk 
they could recover the data.  Multics was only B2 as I recall, they also
had an A1 system (though what you could actually use it for I don't know :-)

--sjg