Before you begin…
Before jumping in, there’s a bit of terminology you should know. First, hard disk and hard drive have the same meaning. But people often use other terms like delete and format interchangeably, while they’re actually quite different.
Delete: Deleting data actually just moves it into a folder, out of sight, like the Recycle Bin in Windows or the Trash on Mac. While still 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. That means 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 the files using data recovery software. The more recently the files were deleted, the more likely it is that you can 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. If you want to use the device again (or sell it), you’ll probably want to use the former method.
Format: Depending on your operating system (OS), you’ll probably have a few options available. Generally, a quick format will simply delete the data on the drive, while a normal format will erase everything (wipe the drive). The drive in question 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. This ensures that you don’t end up with corrupted files down the line.
Reformat: Some people use the term reformat — it’s the same as format!
Now that we’ve got that down, there are a few more things you should know about the formatting process, for both Windows and Mac computers.
Identify which type of hard drive you have
There are different types of hard drives you may be looking to reformat.
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 take the form of a flash drive (also called thumb drive or USB) or a larger enclosure that can contain either a solid-state drive (SSD) or hard disk drive (HDD).
Choose the right file system
Now that you’re clear on the differences between erasing and wiping, and between internal and external drives, it’s time to select a 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: If you want to format your primary drive (which contains your OS), you must use NTFS (NT file system), which is the default 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 your best bet if you want to transfer a large file. So if, say, you want to put a movie on a USB drive to play it on your TV, you should use NTFS. Also, NTFS allows you to set advanced permissions, which can come in handy.
FAT32: FAT32 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.
Both NTFS and FAT32 will eventually become fragmented, meaning you’ll need to occasionally defragment them.
If you’re using 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.
OS Extended (HFS+) was used from 1998 to 2017, but was replaced by APFS.
If you want to move files between Windows and Mac, go for exFAT.
Now that you’ve selected the appropriate file system, let’s get formatting! (Skip ahead for Mac instructions).
How to format a hard drive on Windows
Formatting a hard drive on Windows is largely the same whether you’re using Windows 10, 8, or 7. But it’s a little different if you’re formatting the primary drive vs. a secondary internal drive or an external drive.
How to format a primary (C:) drive on Windows
Recall that the primary drive, or C drive, contains the operating system. That means you can’t format the primary drive while it’s running, for the same reason that you can’t repair a motorcycle’s engine while you’re riding it. So how can we get around this? 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.
Got your Windows 10 or Windows 7 startup DVD on hand? Great, 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, we’re ready to proceed.
Insert the Windows 10 or Windows 7 startup DVD or make sure your bootable USB drive is plugged in.
Reboot your PC.
The Windows startup app should launch automatically; if not, you’ll see a message that says Press any key to boot. Do so, and you might see a message that says Windows is loading files.
The Windows setup wizard will launch. Select your desired language and time, and click Next.
Click on Install now and then wait while Windows completes some setup procedures. Note that Windows is not actually installing, so don’t worry if you don’t have a product key (and if necessary, select the box for no product key).
Follow the next steps to choose your desired version of Windows and accept the terms. When you’re 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.
On the next screen, select Format. It will ask you where you want to install Windows. Select the Primary drive and click Next.
Click Format and Windows will warn you 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.” So you want to make sure that you’ve correctly selected your primary (or C) drive and that you’re okay with deleting all the data on it. Click OK if you’re sure.
Your mouse will show a busy sign during the formatting process, and will then turn back into an arrow once it’s complete. (That’s the only sign that the formatting has been completed.)
At this point, your drive is formatted, and everything is gone! But now you don’t have an OS on your computer.
Reboot your computer.
Download Windows OS from your DVD or USB drive.
How to format an internal or external drive on Windows
Your Windows hard drive may be partitioned into several different drives. Aside from your primary C drive, you may have smaller internal drives with names like D, E, F, etc. External drives are, again, hardware like USB drives or other external storage devices. Luckily, it’s much easier to reformat all of those drives, because they don’t contain the OS.
Here’s how to format either an internal or external hard drive:
Start up your computer as usual, but hold down the WINDOWS key and type in R to open the Run dialog box.
When the box opens, type in diskmgmt.msc and then click OK.
The Disk Management window will open. Select the drive you want to format (internal or external) by right-clicking and choosing Format…. You can also rename drives here if you wish.
A Format box will pop up. That’s where you'll choose the file system for your drive. (See above for our guidance on file systems.) You’ll also have the choice to do a “quick” format or not. A quick format is — wait for it — quick. It’ll do a basic delete of the hard drive in just a few seconds, but it doesn’t truly erase or wipe anything, meaning that it’s out of sight but not irretrievable. It’s a good option if you want to clean the drive, but also want to continue using it yourself. 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. 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. Click OK and you’re done!
If you need to format a drive simply for the purpose of using 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’ll be able to select NTFS, FAT32, or exFAT.
While formatting your disk will wipe it clean, it also deletes your files. If you’d prefer to keep your disk clean without taking the nuclear option, you can perform some disk maintenance instead. Why is this necessary? During the normal computing process, Windows accumulates a ton of junk that bogs it down: residual files, leftover installers, temporary files, cached data, and more. If you don’t clear it out regularly, your machine will start to slow down, freeze, and serve up error messages. Need some help with that? AVG TuneUp fixes and maintains your PC automatically so your drive stays nice and clean.
How to format a hard drive on Mac
Formatting a hard drive for Mac isn’t rocket science, but I wouldn’t let your neighbor’s first-grader do it for you, either.
Here’s how to format a hard drive on Mac:
Start up your computer and log in.
Open Finder, click the Go drop-down menu, and select Utilities.
Then select Disk Utility.
Here you’ll be able to select the hard drive you want to format.
Click Erase to format the drive. A window will pop up 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).
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 basically the same as formatting internal drives. Luckily, that means learning how to format an external hard drive is fairly straightforward. See above for our step-by-step instructions on Windows or Mac. And remember that if you want your external drive to be both Mac and Windows compatible, your best bet is to 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 do a number of things:
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 whole 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 well on your machine, you can format the drive and reinstall the OS to try to simulate a new computer environment. Just make sure to back up the files you need (or clone your whole drive) before you start formatting!
Do new hard drives need formatting?
Nope! New hard drives are formatted automatically, either by default or when you first plug them in. So there’s no secret sauce to formatting new hard drives — just plug them in and you’re good to go.
How long does it take to format a hard drive?
That depends on which type of formatting you want to do, and on which drive. Recall that a quick format will merely delete files, which doesn’t truly remove them. To completely erase files or wipe an entire drive, you’ll 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. All that clutter will slow down your computer and could cause issues such as crashes and freezes. You can remove everything by completely wiping your drive as we’ve described above — 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. Our 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 and give it a spin to see what’s bogging down your computer, then get rid of all that clutter to bring your machine back up to speed.