How to Erase Unused Hard Drive Sectors

Erasing unused sectors will prevent deleted file recovery.
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Even when you delete a file and empty the Recycle Bin, files are still recoverable by using specialized recovery software. If you fear deleted files could resurface after deletion, thoroughly erasing unused sectors will overwrite the deleted files to prevent their recovery. Microsoft offers a small SDelete utility that enables you to overwrite unused sectors using the Command Prompt. However, make sure deleted files are emptied from the Recycle Bin, or the sectors in which the files reside will not be considered unused.

Download "SDelete" from Microsoft (see link in Resources). The executable is provided in a ZIP-compressed file, so you'll need to extract the file.

Press "Win-E" to open File Explorer, double-click the "" file to open it and drag-and-drop the "SDelete.exe" file into the "C:/Windows/System32/" folder. Alternatively, select the "SDelete.exe" file, press "Ctrl-C," navigate to the "C:/Windows/System32/" folder and press "Ctrl-V" to copy it. If you get a security warning, click "Continue."

Press "Win-X" to open the Windows 8.1 Utilities menu and select "Command Prompt."

Type "sdelete -z c:" and press "Enter" to write zeros to all unused sectors in the Windows "C" partition. Alternatively, type "sdelete -c c:" to similarly clean unused space, but using the "-z" command offers greater security by overwriting files with random data. To specify a different hard drive partition, replace "c:" with the drive letter of the partition, followed by a colon.

  • If you receive a pop-up window asking you to agree to the terms of the software, read the terms and click "Agree."
  • Right-click the "Recycle Bin" icon from the Windows 8.1 desktop and select "Empty Recycle Bin" to move all previously deleted files to unprotected sectors.
  • Depending on your settings, you may not see the file extensions for the SDelete files, but you can recognize the file from its folder icon and the SDelete.exe file from the executable icon, which looks like a window pane.

C. Taylor embarked on a professional writing career in 2009 and frequently writes about technology, science, business, finance, martial arts and the great outdoors. He writes for both online and offline publications, including the Journal of Asian Martial Arts, Samsung, Radio Shack, Motley Fool, Chron, Synonym and more. He received a Master of Science degree in wildlife biology from Clemson University and a Bachelor of Arts in biological sciences at College of Charleston. He also holds minors in statistics, physics and visual arts.