[meatloaf]

Even after erased and written over, data can be retrieved. The only sure way of ensuring data cannot be retrieved is to place the hard drive in a furnace and reduce it to molten metal.

[Glenn]

Even after erased and written over, data can be retrieved.

If you do it properly, there will be no data to retrieve. It's a myth that the data is still out there in some ghost-like fashion.