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How does formatting work in Windows?

Does it erase all the data on the drive to 0? What's the difference between fast format and normal format? If it doesn't set all the data in the drive to 0, how can I do that?

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migrated from Nov 18 '09 at 9:33

This question came from our site for professional and enthusiast programmers.

Is this to dispose of the Hard drive or to start from scratch with a new install? are you looking to re use this hard drive or dispose of it in a way which nullifies any data being leaked? – ThunderToes Sep 4 '14 at 13:10

A fast format (sometimes called quick format) only recreates the necessary table structures for the filesystem. The files aren't actually deleted, but when the table structures are reset to it's initial state they will be overwritten in time. This is because the system marked those positions as 'writable'.

A normal format recreates the table structures and clears out every block on the hard drive.

You can manually set the blocks to zero if you want using a tool like 'dd' on Linux.

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I've found that the normal format does not actually clear the blocks either (at least on Windows 9x). It appears to access them all (since it takes so long to run), but at the end of it I was still able to directly read the sectors and pull old data. – Brian Knoblauch Nov 18 '09 at 12:35

If it doesn't set all the data in the drive to 0, how can I do that?

neither quick nor full format will erase data on a hard drive beyond recovery, you want to run Darik's Boot And Nuke (aka DBAN) to be sure all data on the hard disk are wiped thoroughly.

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DBAN also wont work for the DCO and HPA sectors of a hard drive. – Steam Oct 5 '13 at 22:52

A long format will run a short format and a check disk operation.

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There are 3rd party "Wipe Disk" tools that can really erase the data on the disk.

you can start looking here and google the rest:

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When you choose to run a regular format on a volume, files are removed from the volume that you are formatting and the hard disk is scanned for bad sectors. The scan for bad sectors is responsible for the majority of the time that it takes to format a volume.

If you choose the Quick format option, format removes files from the partition, but does not scan the disk for bad sectors. Only use this option if your hard disk has been previously formatted and you are sure that your hard disk is not damaged.

If you installed Windows XP on a partition that was formatted by using the Quick format option, you can also check your disk by using the chkdsk /r command after the installation of Windows XP is completed.

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A Quick format will only wipe out the file-system tables (MFT). Files can still be reconstituted.

A Full format will also rewrite all sectors in order to reset all magnetic platters, thereby wiping out all data. Files can no longer be reconstituted, except with special equipment to "peel back" the magnetic layers, which is only in the possession of organizations such as the FBI, CIA etc.

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