Erasing Files and Hard Drives Securely

If you’re planning on recycling, donating, or even scrapping your old PC, it’s important to ensure that you’ve securely erased all data from your hard drives. Too many people make the mistake of simply formatting the drives prior to getting rid of their old PC, thinking that their personal/business data has been safely erased. Even harder to imaging is the fact that many people don’t bother to delete anything prior to casting their system off into the wilds. If you’re even the least bit interested in maintaining your (or your company’s) privacy, you’ll want to give your system a good scrubbing before it heads out the door.

I know. Who in the world could care less about your old data? Unfortunately, the answer that question is that you just never know. Most users rid themselves of an old PC by giving it to a friend, dropping it off at a recycling facility, or donating it to a charitable cause. Many of these systems in end up in the hands of normal people who will simply format the drive, install an operating system and programs, and be on their merry way. However, there are some people who just can’t help but be nosy, and will take the time to rummage through the hard drive first.

What’s that you say? No worries because you made a point of formatting all of the system’s drives? Sadly, this is the technique used by most users to clean up their data, but unfortunately it does nothing to truly wipe the drive free. A format simply deletes partition tables, with all data still stored in clusters on the disk. Any undelete program will be able to quickly scan the drive, and though it might not find all of your files, it certainly will find its fair share and be able to recover them easily.

Rather than run the risk that the next user of your PC will be able to sift through personal information about you (including credit card information, email messages, and documents), its important to “scrub” the drive to be sure that all of your data has been safely deleted. It’s simply better to be safe than sorry.

Secure Erasing Methods

Without getting into the specifics of data scrubbing techniques ands methods in too much detail, the basic premise of scrubbing a drive involves overwriting every sector on a disk to be sure that the previous data stored on the drive cannot be read. The most basic (and fastest) method involves overwriting every sector on the disk once with repeating values. This technique makes it difficult (but not impossible) for data to be recovered using software or hardware methods. For perspective, the US government (DoD) considers a disk to be “clean” (unrecoverable) after 7 overwrite passes on the entire disk. However, users very serious about ensuring that data is unrecoverable should use the “Guttman” method, which involves overwriting the disk an incredible 35 times. Most commercial data scrubbing applications support up to at least 35 passes, and some even more.

Two popular tools commonly used to scrub drives are Drive Scrubber from iolo technologies and Eraser, a free tool that can be downloaded from

Because Eraser is freeware and one of the most popular tools available, it’s definitely worth a closer look. Eraser includes a tool to securely scrub hard drives using a bootable floppy disk (Darik’s Boot and Nuke) as well as a Windows utility that allows you to securely delete files or scrub free space on your existing partitions.

Boot and Nuke

As the name would suggest, Darik’s Boot and Nuke is a very dangerous tool. After using the WinImage extractor to create the “nuke” boot floppy disk, you then reboot the target system with the disk in drive A. The main point of this program is to securely delete everything, so NEVER run it on a system that you intend to use again.

Files and Free Space

Finally, installing Eraser also provides you with the main Eraser application (see annotation) which allows you to create tasks that will securely delete files and clear disk space on-demand or according to a schedule. It even adds handy shortcut menu items to permanently erase files and clear disk space quickly and effectively – just be careful!

Author: Dan DiNicolo

Dan DiNicolo is a freelance author, consultant, trainer, and the managing editor of He is the author of the CCNA Study Guide found on this site, as well as many books including the PC Magazine titles Windows XP Security Solutions and Windows Vista Security Solutions. Click here to contact Dan.