Besides theoretical documents talking about it, I have been unable to find anything that will recover data on a wiped drive. Now, I am talking about programs that can be purchased, but most of the data recovery people also have data destruction programs that all say once you run this there is no way to recover the data. I'm guessing if the FBI is after you, they might have some tools up their sleeves, but most people don't have multi-million dollar clean room labs to ATTEMPT to recover partial data from your drive. As far as the sensitivity of head reader built into your drive, it wouldn't make much sense for the drive manufacturer to create something that reads files that have been overwritten. If that were the case, every time the drive got full (or you had written/deleted enough to make it full), all your new files would have parts of the old files on them. Unless I'm mistaken, we're talking about something with essentially 2 states. 0 or 1. Now the theoretical stuff is about the ability to read something that is 0.0001 and assume that the last position of that byte was intended to be a 1, not a 0. Now you've got to do that to about 24000 associated bites to create a 3k file. This, of course, is after you have flipped the bites 7 or more times. The idea is that it can be done, but the ability of a user, or even some data recovery center (as they specialize in accidental/failure issues), to do this would be essentially non-existent.
All that being said, if your still worried, the only guaranteed way to destroy data, is to destroy the drive. Fire/acid on the open platter would be best.
