That's why Top Secret data requires destruction. However, any modest effort at wiping the drive will defeat all but the most fanatic. Identity thieves are not fanatics. They're looking for the easy score and wouldn't be interested in putting in a lot of time and a big effort on a drive only to find it contains no or little value.
Total destruction is the ONLY way. Anyone can recover data, not just fanatics and it can be done quickly. DoD wiped data can be recovered. Think I might be wrong? http://downloads.zdnet.com/download.aspx?docid=244321 How much value is there in identity theft? in raiding trading accounts? in impersonation? This is "white collar" crime and gangs are now involved in it! IF I was as concerned about it as the OP, I would move all the data to one folder on the drive. DoD wipe the slack areas several times. Then DoD wipe the data within the folder several times and then steganography or 256 bit encrypt the folder or both depending on the level of paranoia .
There seems to be some confusion over this whole issue. 1. Data isnt written to the Hard Drive in "layers" The hard drive contains locations where data can be stored. When you delete a file the data isnt removed but rather the space that the data is occupying is now marked as useable...meaning you now have more disk space available but the file you thought was deleted is still there in its location where it was written, but if that space was to be over written again by another file then the original file can never ever be retrieved. The freeware programs would do a good job...the idea of writing multiple times isnt like cleaning a dirty mark untill its finally gone but rather some drive whiping programs write patterns to the drive so multiple goes at it ensure completeness....but no better than filling a drive with useless information then deleting it all as after that all you could hope to retrieve is the useless information. 2. No one would bother going to the trouble of looking for data on your old drive. Its no trouble ! Data recovery programs are free and fast...taking from just minutes to a few hours. One single accounting backup file could yield years and years of personal data. The chances of someone doing it though is pretty small but why take the chance...you just have to ask yourself would be the worst that could happen if someone retrieved the data....and if theres not too much to worry about then so be it...but if you have got all your banking passwords on there or similar then why on earth would you not make sure your data is properly removed especially if you have no idea where the P.C. is going to end up after you.
yes, it seems total destruction is the only way because all things/events are recorded on the subatomic level.
Replace the drive with a new one. Keep the drive with your data as a backup drive for a new computer.
I am not concerned about the "manufacturer" doing anything/ . What I am concerned about is The pc will be sold to god knows who. I am concerned about someone who ends up with my pc. get it? Not the manufacturer.
When you need to clean out your old PC just call in a pro...... http://upload.wikimedia.org/wikipedia/en/f/f0/Eraser_Poster.jpg