Over the years I have accumulated a number of old PC hard drives. Some were mine, other from neighbours & friends who asked if I could "fix their PC". It occurred to me that I had a burden of responsibility for these disks, if someone got hold of them they might be able to extract confidential data. In each case I had determined that the disk was dead or dieing, having failed the manufacturers full surface test (via Ultimate Boot CD - UBCD), but conceivably the disk could be attached and read on another computer. They might contain personal data - so I decided to put these disks beyond recovery.
First you have to dismantle the hard drive. this involves removing all external stickers from the disk , and with a torx driver (purchased from your local hardware shop - in my case the always helpful W. C. Baker of Fleet ), remove all the bolts which hold it together.
An excellent video of how to dismantle a similar hard drive is here :
Once the disk is in bits then probably the data is beyond economic recovery. I doubt the platters are interchangeable, and they do not appear to have manufacturers model numbers or any markings at all. Putting one of these platters back in a different model of drive is unlikely to make it readable IMHO, though I dare say a Police forensic department or similar could extract data still, should they have a burning reason to do so. But it could take days.
Having dismantled the drive you have a number of useful artefacts :
1) the shiny platters(s).
These are perfect round mirrors. They could be used as small camping mirrors, for bird scares, wind chimes (they ring) but I decided to make them into a solar collector. I went to my local hardware shop (W.C. Baker of Fleet) and described roughly what I wanted to do, leaving out the bit about building a death-ray. It turned out that standard UK plumbing washers are exactly the right fit. These are 1" / 24mm diameter rubber washers of approx 3-4mm thickness, with a hole in the middle. These provide a snug fit for the hole in the centre of all hard drives. Better still the discs can be tilted slightly on the washer fitting, enabling a degree of 
focusing of the beam. I attached all 9 to a piece of wood. this enabled me to fix this unit in my garden and direct and focus the "death ray" onto a specific target. You can see the awesome effect of this in the picture at the top. You can also see how the projected light from the sun was focused onto my wood pile. It did not spontaneously burst into flame BUT you can clearly see the focused beam in the picture and it was noticeably hotter when I dared to put my hand into it. My hope is that, over 
time, it will slowly dry out those fresh cut logs .The other components you have from the disk drive are :
2) A very strong magnet or two - these work as the best fridge magnets you will ever find - you can probably hang the phone book on your fridge with one of these.
3) The disk controller board. This is the circuit board on the back of the disk. If you are lucky you can sell these on eBay, as they contain no data , but may have a resell value for people with the same disk, but a failed controller board. I sold around 1 in 5 and they don't go for much, just a pound or two but that's OK.
4) the drive case - the chunky black part is high grade aluminium and can be recycled at any Alu recycling plant, or by local charities for funds. Near me is an Aluminium recycling plant (T Baker (JNR) Ltd of Farnham) who, if you ask, will donate your recycling proceeds to the Phyllis Tuckwell Hospice, a very worthwhile local charity
5) The drive heads. this is a wonderful looking piece of engineering. I have no particular idea what to do with them. they might be used as strange jewellery or parts of a robotic fancy dress party. I'll save these for future use.
6) Assorted precision fittings and washers which could be used for all kinds of projects, jewellery, collage etc. There are a set of bearings which the drives head unit uses to pivot.
7) The stepper motor. These electric motors require some logic from the driver board to work, so I don't think you can use them as 12v motors. Again - a future use will present itself, but for the moment they provide nice little stress-busters, as rotating the centre part produces a a satisfying little click as it goes round.
8) The disk "lid" i.e the silvered metal sheet which covers the entire disk enclosures top surface, as opposed to the side with the controller board. On closer inspection, once removed, you will see that this appears to be a sheet of metal. In fact if you tap it you see it's heavily damped. My belief is that this is a sandwich of 2 metals and some deadening material to reduce the mechanical disk noise. It probably also has a thread of silicone adhesive running around the entire circumference which made a gas tight seal with the main body. Leave the silicone in place. I have used a couple of these metal pieces to sit CD players on to stop skipping as they seem to act deaden vibrations.
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