How to Low Level Format (Or Zero-Fill) Your Hard Disk

Pretty much all of you will know about hard disk formatting, and we’d hazard a guess that many of you have done a bit of formatting yourselves. But there is a big difference between that and low-level formatting (LLF) which wipes your hard drive on a deeper level, making old data extremely difficult to recover because it formats the physical sectors on the hard drive itself.

An important thing to know is that the meaning of “low-level formatting” has changed over time, and this efficient formatting method has largely been replaced today by something known as “zero-filling.” Here’s everything you need to know about this process and the tools you need to do it.

Low-level formatting formats your hard drive past the point of no return because it wipes all existing sectors on the physical surface of your drive rather than just on the filesystem. It was used in the past to get rid of all existing data on old MFM hard disks permanently – useful if you had sensitive data that you wanted gone forever, were selling your hard drive, or if you had a severe virus, such as a boot-sector virus, which couldn’t be removed using the standard formatting process.

Today, modern (SATA and ATA) hard drives are low-level formatted upon manufacture and can’t technically be low-level formatted again in the same way as old MFM drives used to be. However, there are equivalent processes that carry out similar functions.  The modern equivalent to low-level formatting is “zero-filling”, whereby you replace all data on your hard drive with arbitrary zeros or other characters, making that data deleted and unrecoverable.

Most of the major hard drive manufacturers have their own zero-filling tools, which usually require booting from a CD or USB drive. Click below to download these tools for each manufacturer. The perks of using the dedicated tools made by manufacturers is that they may perform the formatting faster if you use them with the same-brand hard drive. (The whole process can take a good few hours.)

Alternatively, you can use a great little tool called DBAN which you can use with any brand of hard drive and will erase all your existing hard drive data with six passes. That means it will delete and overwrite existing data six times over making recovery almost impossible. Please note that these tools are designed to work with magnetic (SATA and ATA) hard drives, not SSDs.

1. To use any of these tools, you’ll need to create a bootable flash drive. The best tool to do this with is Rufus. Download it, then open it and make sure your settings are like the ones in the image below. Make sure to click the CD icon next to “Create a bootable disk using,” and select the DBAN ISO you downloaded earlier (or the ISO for whichever formatting tool you decided to use).

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2. When you’ve set all the options correctly, click “Start.” Wait for the process to finish, and you’ll now have a bootable flash drive containing your “low-level formatting” tool.

3. Next, reboot your PC and press F8 or F10 repeatedly until your PC asks which device you want to boot from. Select the flash drive, and the formatting tool should open.

4. From this point on, you should be very careful because this is where you have the power to delete data on your hard drive forever. Each of these tools will work slightly differently, so be sure to read about their various formatting options before committing. In the case of DBAN, the best and simplest option to go for is “autonuke” which will instantly go ahead and zero-fill your drive using the default settings.

low-level-format-hard-disk-dban-2

So after all that, the most important things to remember are that “zero-filling” is essentially the modern-day version of the old process of “low-level formatting” and that you should be completely certain that you’re happy to lose the data on your hard drive forever when you do it. It’s a powerful process not to be taken lightly and certainly shouldn’t be used if all you’re looking to do is  reinstall your OS or refresh your computer.

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