Erasing All Data on Drive

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Sometimes one needs to clear all data on a drive, for example, when selling the drive or when throwing it away. On this chapter you can find step-by-step instructions on how to erase all data on a drive.

First, to overwrite completely all data on a drive, it may be required to install the drive on another system because the operating system files cannot be accessed while it is running (this is not of course needed if the operating system if not installed on the drive).

To start clearing the drive, the first thing to do is to delete all files (no overwriting at this point). After deleting the files, it is time to overwrite the unused disk space. The default method for erasing unused disk space is one pass of pseudorandom data, but you may want to change this to increase security - be aware that overwriting unused space on a large drive using multiple overwriting passes may take several hours.

After all data on the drive is overwritten, you should finally use the standard format to clear possible data remaining on the file system table.

With these security cautions, you can be sure that nobody gets their hand on your data by accident. However, if you are disposing the hard drive (i.e. have no plans for it to be used again) and the drive contains really sensitive data, you may want to consider physically destroying the disk platters after overwriting.

If you don't have access to another system, you need to use a file wiper that can be used from a bootable floppy disk. I recommend using GNU/Linux and the dd command, there are also some DOS applications available for the task.

Eraser for DOS

If you need to erase all files and free disk space from your old personal computer you are planning to donate or recycle, and your computer runs DOS, any version of 16-bit Windows or an early version of Windows 95, you can use the DOS file wiper included with Eraser, eraserd.exe.

Note! EraserD is designed to be compatible even with older DOS version, which introduces some limitations. The program only supports files that are smaller than 2GB and cannot overwrite free space on partitions that are larger than 2GB.

After you have created a bootable floppy disk and copied eraserd.exe from Eraser directory to the floppy, boot the computer from the floppy disk and run the following commands to erase all files from your drive and overwrite remaining free space:

A:\eraserd -allfiles C: -passes 3

A:\eraserd -disk C: -passes 1

You can change the number of overwriting passes to use - the commands above define three overwriting passes for files and one pass for free space, which should be fine for most people.

Repeat the procedure for other partitions you have on the drive. You should also reformat partitions after erasing to remove possibly remaining entries from the file system tables.

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