I,m curious...

[briareus]

-> Thanks everyone for the edumacational posts. Enlightening.

-> Two points I'd like to make: First, all magnetic devices have a 'half-life' for the magnetically readable/writeable components to be readable/writable. This half-life varies with the product and its make-up (i.e. the iron oxide [rust] read/write layer in an average floppy has about a 5 to 7 year half life, while your HD will have a much longer half-life)... as with any tech question, always start by reading the documentation for your device.

-> Second, the NSA recommends AT LEAST a seven-time data overwrite of random bits to erase "SENSITIVE" classified data, so you can bet higher classifications like SECRET or SIGINT-UMBRA will require more, perhaps many more.

[Ultra]

You cannot destroy everything. I read an article in a magazine a while ago, I know you cant always believe them but the only way you can totally erase everything that was on there is by using a certain tool. Even then you have to run it 2 times to get everything.
The FBI has one and when they destroy a harddrive they send it through SEVEN times. Some may see this as overkill but when you are in their game you cant afford to take chances.