Formatting a computer's hard drive is an important step if you're disposing of it and wish to remove all your personal data, and also if you want to completely remove an old Windows installation. We explain how to use tools built in to Windows to completely wipe a PC or laptop drive.

Note that the process can be different depending on whether it's your only hard drive and whether you have a spare PC or not. You can't, for example, format the hard drive on which Windows is running. In order to do this you will need to boot your PC from a Windows installation disc, a USB flash drive or another bootable drive.

How do I completely wipe my hard drive?

When you format a drive, it frees up space for new files. But there are a different types of formatting. Beware of 'Quick Format' which leaves all your data in place and makes the drive appear to be empty. It's just a fast way of wiping the drive which is fine if you're going to reuse it yourself, but not if you're disposing of the disk or giving it to someone else.

In fact, if you are disposing of the drive or passing it on to someone else it's worth securely erasing the contents to make sure no personal information can be recovered.

Warning: make sure you have backed up any photos, videos, music and other documents from your drive before you format it. Although deleted files can be recovered in some situations, it's best to assume that no files will be accessible once you have used the techniques below.

The right way to format a hard drive or in Windows is as follows, but if you do have an SSD, then check its manufacturer's website as there might be a specific tool available for formatting it.

Type diskmgmt.msc or Disk Management into the search box, or if you have Windows 10 press Win+X then K. 

That's the easiest way to launch Disk Management, but you'll also find it in the Control Panel if you search for 'disk' and select the 'Create and format hard disk partitions'.

Disk Management isn't as powerful as a standalone partition management tool such as Paragon Hard Disk Manager, but it is still capable of formatting drives.

Right-click on the drive you want to wipe and click Format...

As you can see below, this will only affect the portion (called a partition) of the disk that you select. Sometimes a partition will use up the entire disk, but there may be several partitions on one disk.

How to format a hard drive

Type a name for the drive next to Volume label, and choose which file system you'd like the drive to be formatted with. If it's an internal hard drive, you'll want to use NTFS. Leave the allocation size set to default. Uncheck 'Perform a quick format' if you are disposing of the drive, otherwise the data won't actually be deleted.

How to format a hard drive

Click OK and you will be asked if you're sure you want to wipe the drive, so confirm that you do and the drive will be formatted.

How do I format a new hard drive?

When you install a new (additional) hard drive in your PC, you might wonder why it doesn't appear in Windows. The reason is because it needs to be initialised and formatted. Again, you can do this in Disk Management.

As Disk Management loads, it will analyse all your computer's drives and will prompt you to initialise any new disk that it finds.

Initialize disk

You should opt for GPT (GUID Partition Table) if your laptop or PC is modern and has a UEFI BIOS, or your drive is 2TB or bigger.

If you don't see a prompt, look in the list of drives and you should see one that says 'Not Initialized'. Right-click on it and choose Initialize Disk.

Once that's done, right-click in the hatched Unallocated space and choose New Simple Volume…

Follow the instructions, choosing how big you want the partition to be (in MB - 1024MB = 1GB), and which drive letter you want (one will be chosen, but you can opt to change it if you wish).

When you come to format the partition, our advice is the same as in the Quick Format section above.

If you select a size for the partition that's smaller than the total capacity of the drive, say 500B on a 1TB drive, you'll end up with some unallocated space on the drive which you can format by repeating the process you've just completed.

Can I format a hard drive from the BIOS?

Many people ask how to format a hard disk from BIOS. The short answer is that you can't.

If you need to format a disk and you can't do it from within Windows, you can create a bootable CD, DVD or USB flash drive and run a free third-party formatting tool.

One option is Darik’s Boot and Nuke (DBAN), which is free for personal use. This program will totally erase and format your hard disk, but does not support secure erasing of SSDs. 

How to format a hard drive

DBAN is supposedly only able to create a bootable CD/DVD-R, but if you don’t have any blank discs or a burner, there is a workaround available in the form of a separate third-party program.

Universal USB Installer will quickly and easily convert the DBAN ISO image you downloaded to run from a bootable USB. Simply insert a blank USB flash drive, run the Universal USB Installer setup program, and follow the prompts.

You will be asked to scroll through and pick the Linux Distribution you want to install to USB (in this case, the latest version of DBAN), followed by its location on your computer and the letter of the USB drive you’d like to install it to.

Once that information is complete, click create.

How to format a hard drive

To boot from this USB drive rather than your usual boot device (in most cases, this would be the hard drive), you’ll have to change some settings in the BIOS. If you’re not sure how to access the BIOS menu, read our guide on how to enter the BIOS.

In the BIOS, navigate to the boot order settings, and change the primary boot device to the USB drive (it shouldn't need to be plugged in to make this selection). After you’ve saved your settings and exited the BIOS, insert your bootable USB, restart your computer.

How to format a hard drive

Your PC should automatically boot the DBAN software, which will guide you through the process of erasing your hard drive, with options for different levels of data-wiping.

It will treat the USB as another drive so to avoid inadvertently wiping that as well, remove it after you’ve booted into DBAN.

How do I format a RAID drive?

If you have two or more disks configured as a RAID, there are various ways to format these drives. Before you use any of them, make sure you back up any files you want to keep.

  • Use a software utility which came with your RAID controller or motherboard.
  • Go into the RAID controller's BIOS (look for a message during PC boot up) and look for an option to format the drive(s) or reconfigure the RAID as individual disks (this will erase them all).
  • Unplug the drive you want to format and connect it to a different SATA port on your motherboard which isn't part of the RAID controller. Then, follow the Windows Disk Management method below since the disk won't be visible in Windows Explorer.

Can I quick format a hard drive?

Yes, but don't use this method if you want the data to be permanently erased. A quick format doesn't delete the data but instead erases only the pointers to the files.

This is the fastest, but least secure way to format a hard drive. Open a File Explorer window (Win+E) then right-click on the hard drive you want to wipe. You can't format the drive on which Windows is installed for obvious reasons.

Choose Format… from the menu and a new window will appear with a few formatting options. As a note: Windows 8 users will need to search for 'This PC'.

Quick format a hard drive

By default Quick Format is checked, and you can choose the file system and allocation unit size as well as changing the volume label (the drive's name). Typically, you can leave all settings unchanged and click the Start button. In under a minute your hard drive will be formatted.

Format options

You should choose NTFS as the file system for internal disks, and EXFAT for large-capacity removable drives - and ensure the Allocation Unit Size is set to 'Default'.

How to change partition size

You can use Disk Management to expand or shrink a partition. Simply right-click on one and choose the appropriate option from the menu that appears. If shrinking, the partition will be checked to find out how much empty space it contains.

Shrink a partition

It's a little confusing as the numbers are displayed in MB rather than GB, but you can adjust the amount of space to shrink and the 'Total size after shrink' will be updated. You can't shrink a partition beyond the point where files are located - you may be able to free up space by defragmenting the drive first.

Conversely you can only expand a partition if there is unused space on the drive. If not, the option will be greyed out.