AVG Signal Blog Performance Hardware Ultimate Guide: How to Format a Hard Drive
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If you know which drive you want to format and which file system to choose, then go immediately to our instructions for formatting a hard drive in the following section.

If not, skip down to read about the differences between formatting a primary and secondary drive, and make sure you learn about the relevant file systems — NTFS, FAT32, exFAT, and APFS — and understand which one to choose.

This article contains:

    How to format a hard drive on Windows

    Formatting a hard drive on Windows is largely the same whether you’re using Windows 10 or 7. But it’s a little different if you’re formatting the primary drive, a secondary internal drive, or an external hard drive.

    How to format a primary drive (C:) on Windows

    Your C drive (C:) is your primary drive where the operating system (OS) is located. You can’t format the primary drive while it’s running, for the same reason that you can’t repair a car engine while driving. To get around that, we’ll run Windows from an installation DVD or a USB drive. That means your primary drive won’t be in use, so we’re able to work on it.

    Note that this process will delete the OS and all files, but it won’t permanently erase them. (Read about deleting vs. erasing below.)

    If you have a Windows 10 or Windows 7 startup DVD, you can skip the next paragraph.

    If not, you’ll need to create a bootable Windows USB drive. Make sure you have an external USB (also called a thumb drive or flash drive) ready. Then, download the software you need:

    For either Windows 10 or 7, follow the instructions to create the bootable USB drive.

    Now that you have either the startup DVD or the USB, you’re ready to format your drive. Here’s how to format your primary hard drive on Windows 10 or 7:

    1. Insert the Windows 10 or Windows 7 startup DVD or make sure your bootable USB drive is plugged in.

    2. Reboot your PC.

    3. The Windows startup app should launch automatically. If not, you’ll see a message that says Press any key to boot. Do so — you may see a message that says Windows is loading files.

    4. The Windows setup wizard will launch. Select your desired language and time, and click Next.

      Opening the Windows startup wizard
    5. Click Install now and wait while Windows completes the setup procedures. Note that Windows is not actually being installed, so don’t worry if you don’t have a product key (if prompted, select the box for no product key).

    6. Follow the next steps to choose your desired version of Windows and accept the terms. When prompted with a choice of Types of Installation, choose Custom: Install Windows only (advanced) for Windows 10 or Custom (advanced) and then Drive options (advanced) for Windows 7.

    7. On the next screen, select Format. Choose where you want to install Windows. Select the Primary drive and click Next.

      Preparing to format a drive in Windows
    8. Click Format and you’ll see a warning that this drive “might contain important files or applications from your computer manufacturer. If you want to format this partition, any data stored on it will be lost.” Click OK if you know you want to proceed.

    9. Your mouse will show a busy sign during the formatting process, and will turn back into an arrow once it’s complete. (That’s the only sign that the formatting is complete.)

    10. Now your drive is formatted, and everything is gone. But now you don’t have an OS on your computer, so you need to install one.

    11. Reboot your computer.

    12. Download Windows OS from your DVD or USB drive.

    How to format an internal or external drive on Windows

    Aside from the primary C drive (C:), you can also format an internal drive or an external hard drive. Your Windows hard drive may be partitioned into several different drives. Smaller internal drives with names like D, E, F, etc. are your internal drives. An external drive is hardware like a USB drive or another external storage device.

    It’s much easier to reformat all of those drives, because they don’t have an operating system. The process is the same for internal (non-C) drives and external drives.

    Here’s how to format either an internal or external hard drive:

    1. Start up your computer as usual, but hold down the WINDOWS key and type in R to open the Run dialog box.

    2. When the box opens, type in diskmgmt.msc and then click OK.

      Using the Run dialog box and diskmgmt to prepare to reformat a drive
    3. The Disk Management window will open. Select the drive you want to format (internal or external) by right-clicking and choosing Format…. If you want, you can also rename your drives here.

      Using disk management to format drive in Windows
    4. A Format box will pop up where you can choose the file system for your drive. (See below for our guidance on file systems.) Decide if you want a quick format vs full format. Click OK and you’re done.

      Selecting a file system before reformatting the drive

    What’s a “quick” format? This faster formatting option will do a basic delete of the hard drive in just a few seconds, but it doesn’t truly erase or wipe anything, meaning that the data is out of sight but not irretrievable. Quick formatting is a good option if you want to clean the drive but also want to continue using it.

    If you’re preparing your computer before giving it away or selling it, you should do a normal format by unchecking the Perform a quick format box in the step above. This may take several hours, but will more thoroughly wipe your personal information. It will also scan and remove any bad sectors, which prevents future corrupted files.

    If you need to format a drive to use a different file system, you can quickly do that from the Windows Explorer screen. Just right-click on the drive and select Format. From there, you can select NTFS, FAT32, or exFAT.

    Formatting a drive quickly from the Windows Explorer screen to use a different file system.

    Formatting your disk will wipe it clean, but it also deletes your files. If you’d like to keep your disk clean without taking the nuclear option, you can perform disk maintenance instead. Try fixing hard drive errors with CHKDSK or fixing 100% disk usage errors in Windows.

    Why is Windows maintenance necessary? During the normal computing process, Windows accumulates a ton of junk that slows it down: residual files, leftover installers, temporary files, cached data, and more.

    If you don’t clean up your drive regularly, your machine can start to slow down, freeze, or serve up error messages. An optimization tool like AVG TuneUp will fix and maintain your Windows PC automatically so your drive stays nice and clean and error-free.

    How to format a hard drive on Mac

    Formatting a hard drive for Mac is pretty straightforward if you follow the steps carefully.

    Here’s how to format a Mac hard drive:

    1. Start up your computer and log in.

    2. Open Finder, click the Go drop-down menu, and select Utilities.

      Open Finder to begin the reformatting process in Mac
    3. Then select Disk Utility.

      Opening Disk Utility from Applications
    4. Select the hard drive you want to format.

      Selecting the appropriate drive to format
    5. Click Erase to format the drive. A window will display to let you choose the file system you want, and how many times you want to overwrite the drive. Multiple overwrites will take longer, but they’re more secure (and will prevent your files from being recovered).

    Identify which drive you want to format

    Before you start the formatting process outlined above, decide which hard drive you want to reformat.

    On Windows, your primary hard drive or C drive (C:) is the internal hard disk where the operating system (OS) resides. You may also have additional internal drives to store more files on your computer. This happens when your disk is partitioned (separated) between the primary drive and additional internal drives.

    An external hard drive is located outside of your computer, and it can be a flash drive (also called thumb drive or USB) or a larger drive that can contain either a solid-state drive (SSD) or hard disk drive (HDD).

    Choose the right file system

    File systems are rules that govern how an OS stores and reads files. When you format a hard drive, you’ll be asked to choose your desired file system.

    If you’re using Windows, you can choose between NTFS, FAT32, and exFAT.

    • NTFS file format: If you want to format your primary drive (with your OS), you must use NTFS (New Technology Files System), the default and modern Windows file system. NTFS is also a good choice for external drives, because it’s compatible with a wide range of devices.

    • With basic file security and support for files over 4 GB in size, NTFS is the best option when transferring large files. If you want to put a movie on a USB drive to play it on your TV, you should use NTFS. Also, NTFS lets you set helpful advanced permissions.

    • FAT32 file format: FAT32 (File Allocation Table 32) is an older file system dating back to Windows 95. It’s compatible with the largest range of file types, but it can’t store anything over 4 GB.

    • exFAT: The exFAT (Extended File Allocation Table) file system is designed for removable storage like USB drives, SD cards, and other external hard drives. It’ll let you transfer files between different operating systems. Use the exFAT file system if you want to move files between Windows and Mac devices, or if you want your files to be compatible on both operating systems.


    Eventually, both NTFS and FAT32 will become fragmented, meaning you’ll need to occasionally defragment them.

    If you have a Mac, you’ll generally use the APFS (Apple File System).

    • APFS became the default file system when macOS High Sierra was introduced. It’ll work on all types of hard drives, but is optimized for flash-based storage, including SSDs. From 1998 to 2017, HFS+ (the Hierarchical File System Plus, also known as Mac OS Extended or HFS Extended) was used, but it was replaced by APFS.

    After selecting the appropriate file system, you can start formatting. Jump back up to learn how to reformat a hard drive on Windows or get formatting instructions for Mac.

    What about formatting external hard drives or flash drives?

    The steps to format external drives and flash drives (also called thumb drives and USB drives) are the same as formatting internal drives. That means that learning how to format an external hard drive is fairly straightforward.

    See above for our step-by-step instructions on formatting drives on Windows or Mac. And remember that if you want your external drive to be both Mac and Windows compatible, use the exFAT file system.

    What does formatting a hard drive do?

    Why format a hard drive? As mentioned above, formatting a hard drive can help with a variety of tasks.

    • Quick format: Deletes or overwrites your files, which is closer to hiding them than removing them for good.

    • Normal format (also called reformat): Erases your files and completely wipes the drive, making it much more difficult to recover. This is the best option if you want to sell or give away your computer or external storage device.

    • Start from scratch: If things are no longer working on your machine, you can format the drive and reinstall the OS to try to create a new computer environment. Make sure to back up the files you need (or clone your hard drive) before you start formatting.

    Is formatting the same as deleting, erasing, wiping, reformatting?

    Hard disk and hard drive have the same meaning. But people often use other terms like delete and format interchangeably, but they’re actually quite different.

    • Delete: Deleting data just moves it into a folder, out of sight, like the Recycle Bin in Windows or the Trash on Mac. While in that folder, the files can be recovered easily. If you empty the Recycle Bin or Trash, the files can then be overwritten by new data.

      When your device needs to save new data, it can (and will) use the space occupied by the deleted files. Before they get overwritten, though, you can still recover deleted files using data recovery software. The more recently the files were deleted, the easier it is to recover them.

    • Erase: Erasing or scrubbing a file gets rid of it for good.

    • Wipe: Wiping refers to erasing everything on a given storage device or hard drive. As with erasing, you can use data destruction software — or just break out a hammer, unless you want to use the device again.

    • Format: Depending on your operating system, you should have a few options available for formatting. A quick format will simply delete data on a drive, while a normal format will erase everything (wipe the drive). The drive can be your hard drive, or a removable drive such as a USB. A full format will also scan your disk for any bad sectors and remove them, ensuring that you don’t end up with corrupted files later on.

    • Reformat: When talking about hard drives or external drives, the term reformat means the same thing as format.

    Do new hard drives need formatting?

    No. New hard drives are formatted automatically, either by default or when you first plug them in. So you don’t need to learn how to format a new hard drive — just plug your drive and you’re good to go.

    How long does it take to format a hard drive?

    Formatting a hard drive can be a quick or long process, depending on which type of formatting you do, and on which drive. Recall that a quick format simply deletes files, which doesn’t truly remove them.

    To completely erase files or wipe an entire drive, you need to do a normal format (also called a normal reformat). It’s a more thorough process that can take several hours, depending on the size of the drive and how much data it contains.

    Keep your hard drive performing at its best

    Over time, your hard drive becomes cluttered with temporary files, cached data, duplicate files, apps you never use, and other junk files. All that clutter will slow down your computer and can cause crashes and freezes.

    You can remove everything by completely wiping your drive — but that’s not a long-term solution. The same junk data will quickly build up again with regular computer use.

    A better option is a dedicated cleaning tool such as AVG TuneUp, available for PC and Mac. AVG TuneUp’s Disk Cleaner and Browser Cleaner features will regularly scrub your machine clean of leftover junk data for a faster, better computing experience.

    Download our free trial right now to see what’s clogging up your computer, then get rid of all that clutter to bring your machine back up to optimal speed.

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