Perhaps put HDD in a long planter pot (like a window box), to contain the reaction?

1. aluminum and aluminum oxide are toxic to humans. don’t breathe it. don’t eat it. that said, using thermite to destroy an HD presents less toxic materials into the environment than the process of making the PC and chassis to begin with, so get a grip, get a life, and don’t buy any more computers if you’re so worried about it.

2. thermite itself is not considered an explosive although it will sputter molten metal in a semi-explosive manner. however, thermite in combination with sulphur, copper and/or magnesium can be used as an explosive. further, the explosive bolts NASA uses for decoupling rocket stages are thermite. further, thermate is explosive, and nano-thermate is highly explosive.

3. the military and intel dispose of HDs in two ways: strong magnetic fields (strong enough to actually warp the platters) and incinerators. acid might be used too, idk.

4. of course it was an inside job, see “The Ghost in the Machines: Evidence of Foreknowledge in the WTC Hard Drive Recoveries” http://journalof911studies.com/volume/2008/GhostWTC.pdf

The rest of you, I admire your intelligence and cunning originality.

On the data recovery side, I’ve done some data recovery, I’ve written encryptions, I’ve read up on the history of data recovery/encryption/etc, I’ve put a lot of effort into researching forensics of computers as this was at one point what I wanted to do for a career. So, taking that all into consideration, I know a fair bit about recovery methods ;) First off, formatting or any software methods for that matter are utterly useless, given enough time you could easily get data back, the only encryption that can perfectly secure data is a One Time Pad, however its just dumb to even consider using one (Wikipedia it if you want to know why)… drilling/sawing/smashing a hard drive into tiny peices is as useful as handing a passworded drive to a PC geek. On a 500GB HDD, a square cm of HDD would give you many gigabytes of data… Degaussing is a good method (which someone mentioned), basically destroying the magnetic field via heat or intense magnetic radiation, there is no logical or theoretical method for recovering data in these cases, so a lot of places do this. Finally, the government and “secret” organisations generally prefer total destruction of a hard drive by using similar things to thermite, purely because whilst no theoretical method exists for degaussed data recovery, its possible someone could find a way some day (and then theres those paranoid people who believe the government can do it but won’t admit it). You’ll also need to completely destroy the RAM, as its been proven that data can be recovered from RAM under certain condition (I believe they extracted data from RAM some 50 hours after the PC was powered off).

At the end of the day, the simple rule of thumb is don’t be a dumbass, stay out of trouble… don’t get caught ;)