I also agree that running drive wiping software (assuming it is any good) is fine for most purposes.
I was just pointing out in my earlier post that given enough time and energy almost anything digital can be recovered (even after most drive wiping software has been run) because of the nature of the media. The only sure way to destroy the data is to physically disassemble the media and damage it in such a way that it cannot be physically reassembled. But if you are going to that level of trouble then chances are that you have backups somewhere which are a lot easier to compromise than the disk is to reassemble.
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