The new instructable is here. Its ia newer, improved and hugely better version and adresses the disadvantages of this design.
If you are a computer guy, you must have lots of Hard Disk drives piling up. If you want to use these for a good reason, the HDD Sander is just for you.
Because of the high RPM platter motor , the HDD platters have enormous speeds, generally from 5000 RPM up to 15,000 RPM. To make use of this power, The HDD Sander attaches directly to the platter, in a portable and interchangeable design.
A quick video of the HDD Sander in action is below.It was taken in the dark and looks excellent, due to the sparks coming from the sander.
WARNING: The HDD sander is not a plaything. The platters are spinning at a very high speed, making it easy for the sander to rub your finger raw. I am not responsible for any damage you do to yourself or to anyone else near you.
UPDATE 1: Some users have pointed out to me that their HDDs are just not simply spining up. To make them, sometimes you need to adjust the jumper blocks on the back of the HDD.See Step 4, Picture 1 for help.
Step 1: Materials
1.An dead HDD - From a old Presario ($0)
2.Sand paper(any grit) - $5
3.A bench-top Power Supply/12v power source - ATX conversion ($0)
(Search for "ATX bench-top Conversion" on instructables)
4.Molex Power Connectors - $0 (recycled from old PSU)
Thats it, thats all you need for the HDD Sander. I expect you to have a few basic tools like a pair of scissors and a wire stripper and a screw driver with a Torx T9 driver head.
You'll also need an compass to make the sand paper template.