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Hard drive disposal.

Just a bit of feedback on the follow up comments. I will use the book anologies i mentioned earlier to help explain the concepts.

Restore factory settings - Assuming you are using a recovery parition like most modern PC's come with. Imagine you had a book with 100 pages, page 1 is your table of contents. Pages 2-20 contain a backup copy of your operating system (Windows) should you encounter any issues and want to revert back to the day when you first bought your pc. These pages should never change and are used for restoration purposes only. Pages 21-100 contain your running copy of windows and any applications, data, spreadsheets, music etc that you have put on your machine. If you choose to restore to factory defaults your table of contents will be updated to say that pages 21-100 are now free. Data will not actually be deleted. Then a clean copy of the operating system contained in pages 2-20 will be copied to somewhere in pages 21-100. Alot of data will get overwritten but you cannot guarantee that will necessarily be your secure documents. Hence some data will likely still be recoverable.


With regards to formatting, their are two types of format.

Quick Format: Simply purges the table of contents page completely so the operating system thinks the book is empty and can write to any page it wishes. Although as mentioned previously all the data is still contained in the book. This process usually takes a couple of seconds because no data is overwritten.

Full Format: Clears the table of contents page and writes zero's to every page effectively making the book blank. This process will usually take a couple of hours depending upon the size of the disk.

Whilst a full format should technically make data unrecoverable experts recommend doing this process numerous times with random data to ensure data is truly unrecoverable hence various algorithms such as the US DOD which writes random data across the whole disk 7 times.

Back to the physical methods.

Smashing the drive does not necessarily guarantee that data is unrecoverable. For sure its a real pain in the ass and unfeasable for 99.9% of people but technically any platters on the disk could potentially still be intact and analyzed under a specialist microscope to obtain any remaining bits and potentially piece back at least some data. I for one would not bother trying to reassemble a disk it depends how sensitive your information is I guess. Make sure its smashed to smithereens.

With regards to magnets yes you can use them on disks, but how can you be sure you have magnetically changed every sector? If you do this make sure you use a strong magnet like a neodymium :)

The problem with the above two methods is that the disk is likely to be unusable at all afterwards, this may be what you want, if so happy days. However using software to write none sense a good couple of times to the disk in every sector should ensure that disk does not contain any sensitive information whilst allowing the drive to be reused aswell as being more environmentally friendly :D

None of the methods above help you if your computer is stolen therefore I would advise if you have sensitive information on your computer you look at some form of disk encryption.
 
Full Format: Clears the table of contents page and writes zero's to every page effectively making the book blank. This process will usually take a couple of hours depending upon the size of the disk.

That depends what OS (Operating System) you are using. It does not apply for example to XP. The newer OS write zeroes and then check if the read is successful.

Look HERE.
 
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In the past a low level format (such as used by fdisk) of the drive remapped the sectors and completely cleared the disk structure.
Modern drives require a Zero Fill Utility to clear the drive, Zero Fill utilities are drive specific and the use of one manufacturer's ZF may cause corruption on another's drive.
Cheers
Guy
 
If you are using Vista or Win 7 you do not need a Zero Fill Utility.

The format command behavior has changed in Windows Vista. By default in Windows Vista, the format command writes zeros to the whole disk when a full format is performed. In Windows XP and in earlier versions of the Windows operating system, the format command does not write zeros to the whole disk when a full format is performed.
 
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