Now I just have to find a sufficiently old/loud harddrive to make this worthwhile (modern ones are so quiet).
They're not so quiet when you have the case off and when you are making the VMC hit the end stops. Hard drives don't normally click because the VCM is controlled so it doesn't hit the end stops. Something like an old 40GB Maxtor works fine (and you can get them from anywhere - they were used an awful lot around the millenium - and many servers/desktops died an early death because of them 
)
Mowcius