Initializing a Hard Drive in Windows 10

To initialize a hard drive in Windows 10, right-click the Start button, select Disk Management, right-click the disk marked Not Initialized, and choose Initialize Disk. Keep GPT (GUID Partition Table) selected and click OK. Then right-click the black Unallocated bar, choose New Simple Volume, and finish the wizard with the NTFS file system. The drive then appears in File Explorer with its own letter.

Only do this on a brand-new drive or one you’re happy to erase. If a drive that used to hold your files suddenly says “Not Initialized,” stop and read If a drive with files says Not Initialized first.

Applies to: Windows 10 (all editions) with internal SATA or NVMe hard drives and SSDs, and external USB drives. The steps follow Microsoft’s Initialize new disks page, which covers Windows 10 and Windows 11. Windows 10 reached end of support on October 14, 2025, and only PCs enrolled in Extended Security Updates still get security fixes, through October 12, 2027.

Before you start

Three terms get mixed up a lot, and knowing the difference tells you where you are in the process:

• Initializing writes a partition style (GPT or MBR) to the disk. It’s the blank map Windows needs before it can put anything on the drive.
• Partitioning (creating a volume) marks out a section of that map. Disk Management calls this a New Simple Volume.
• Formatting puts a file system such as NTFS on the volume so it can hold files.

A new drive needs all three, and Disk Management handles them in two passes: the Initialize Disk dialog, then the New Simple Volume Wizard.

You’ll also need:

• An administrator account. Disk Management changes need admin rights.
• The drive installed and connected. Internal drives need both the data cable (or M.2 slot) and power. External drives should be plugged straight into the PC, not into a hub.
• The drive’s capacity. Check the label or box (for example, 2 TB). It’s the easiest way to pick the right disk in Disk Management, where a 2 TB drive shows as about 1863 GB.

Many external drives and portable SSDs come already formatted. If yours shows up in File Explorer with a drive letter as soon as you plug it in, you don’t need to initialize it at all.

Initialize the disk in Disk Management

1. Open Disk Management. Right-click the Start button (or press Windows key + X) and select Disk Management. You can also press Windows key + R, type diskmgmt.msc, and press Enter. There are a few more routes in this walkthrough for opening Disk Management in Windows 10.
2. Watch for the automatic prompt. When Disk Management finds a new disk, it often opens the Initialize Disk dialog right away with the message “You must initialize a disk before Logical Disk Manager can access it.” If it does, skip to step 5.
3. Find the new disk. In the bottom half of the window, each physical drive has a gray label on the left (Disk 0, Disk 1 and so on). Your new drive usually has the highest number and shows Unknown, Not Initialized and a black Unallocated bar. Match the size to your drive. Disk 0 is normally the drive Windows runs from, so leave it alone.

4. Bring it online if needed. If the label says Offline, right-click the gray label and select Online. Then right-click the gray label again and select Initialize Disk. Right-click the label on the left, not the bar on the right, or you won’t see this option.
5. Check the disk and pick a partition style. In the Initialize Disk dialog, make sure only your new disk is ticked. Under “Use the following partition style for the selected disks,” leave GPT (GUID Partition Table) selected unless you have a specific reason to use MBR (see the next section). Click OK.

6. Check the status. The disk label changes from Not Initialized to Basic and Online. The bar on the right still says Unallocated. That’s expected: the drive is initialized but doesn’t have a usable volume yet.

At this point the drive still won’t appear in File Explorer. Carry on with creating a volume.

GPT or MBR: which should you choose?

For almost every Windows 10 PC sold in the last decade, GPT is the right answer. Microsoft’s own page says GPT is “used by most computers for hard drives and SSDs” and makes it the default.

	GPT (GUID Partition Table)	MBR (Master Boot Record)
Drive size	Uses the full capacity of large drives	Can only use about the first 2 TB (on drives with 512-byte sectors); the rest is wasted
Partitions	Up to 128 on Windows	Four primary partitions, or three plus an extended partition
Booting Windows from it	Needs UEFI firmware and 64-bit Windows	Works with older legacy BIOS PCs
Best for	Any data drive, any drive over 2 TB, modern PCs	Very old PCs, 32-bit systems, or a drive you’ll plug into an older device that doesn’t read GPT

For a second drive that only stores files, GPT works on any 64-bit or 32-bit Windows 10 PC, even one that boots in legacy BIOS mode. The firmware question only matters if you plan to install Windows on the new drive and start the PC from it. Microsoft explains the 2 TB limit in Windows support for hard disks that are larger than 2 TB.

Picked the wrong one? On an empty disk you can switch later: right-click the gray disk label and choose Convert to GPT Disk or Convert to MBR Disk. Those options only appear once every volume on the disk has been deleted, so do it before you copy files over.

Create and format a volume

This turns the black Unallocated space into a drive you can use.

1. Start the wizard. Right-click the black Unallocated bar for your new disk and select New Simple Volume. On the welcome page, click Next.
2. Set the size. On the Specify Volume Size page, the box is already filled with the maximum size in MB. Keep it to use the whole drive as one volume, then click Next. To split the drive (say, one part for games and one for photos), enter a smaller number and repeat the wizard on the leftover space later. For more on splitting drives, see how to partition a hard drive in Windows 10.
3. Pick a drive letter. On Assign Drive Letter or Path, Windows suggests the next free letter, such as D or E. Accept it or choose another from the list, then click Next.
4. Choose the format settings. On Format Partition, keep Format this volume with the following settings selected and set:
   • File system: NTFS for an internal drive or any drive used only with Windows PCs. If you’ll move an external drive between Windows and a Mac, exFAT is the usual choice.
   • Allocation unit size: leave it on Default.
   • Volume label: type a name you’ll recognize, like Storage or Photos. This is the name you’ll see next to the letter in File Explorer.
   • Perform a quick format: leave it ticked. On a brand-new drive, a full format only takes much longer.
   Click Next.

5. Finish. Review the summary and click Finish. The bar shows Formatting for a few seconds (a quick format) and then turns blue.

Windows may open the new drive in File Explorer straight away. That’s a good sign, not an error.

How to tell it worked

• In Disk Management, the new disk’s bar is blue (not black) and reads something like Storage (E:), the size, NTFS, and Healthy (Primary Partition).

• In File Explorer, select This PC. The drive is listed under Devices and drives with nearly all of its space free. If you can’t spot it, these tips on finding drives in File Explorer help.
• As a final check, create a folder on the drive and copy a file into it.

If the size looks smaller than expected, remember that Windows counts in binary units, so a 1 TB drive shows as about 931 GB. That’s normal. If a 3 TB or 4 TB drive only shows about 2 TB of usable space, it was initialized as MBR; see Troubleshooting.

Alternative: initialize with DiskPart

DiskPart is a command-line tool built into Windows. It’s useful if Disk Management won’t initialize the disk or keeps freezing. It also has no undo and no confirmation prompts, so read this before you start.

Warning: The clean command below removes all partition information from whichever disk is selected. If you select the wrong disk number, you’ll wipe that drive, including the one Windows is on. Unplug any other external drives you care about before you begin, and use the size column to identify your disk.

1. Type cmd in the search box on the taskbar, right-click Command Prompt, select Run as administrator, and then select Yes.
2. Type diskpart and press Enter. The prompt changes to DISKPART>.
3. Type list disk and press Enter. Find your new drive by its size. In this example it’s Disk 1.
4. Type select disk 1 (use your own number) and press Enter. Then type detail disk to double-check the model name and confirm it has no volumes.
5. Run these commands one at a time, pressing Enter after each:
   • clean (clears any existing partition information)
   • convert gpt (or convert mbr)
   • create partition primary (uses all the space)
   • format fs=ntfs quick label=Storage
   • assign (gives it the next free letter; use assign letter=E to pick one)
6. Type exit to leave DiskPart.

If the disk shows as offline or read-only in detail disk, run online disk and attributes disk clear readonly before clean. Microsoft documents each command in its DiskPart clean reference and convert gpt reference; note that convert gpt only works on an empty disk, which is why clean comes first.

PowerShell users can do the initialization step with the Initialize-Disk cmdlet. Run Get-Disk first, find the disk with a partition style of RAW, and then run Initialize-Disk -Number 1 -PartitionStyle GPT with your own disk number.

Troubleshooting

If a drive with files says Not Initialized

Don’t click OK on the Initialize Disk prompt. Click Cancel. Initializing replaces the partition table, so Windows will treat the drive as empty, and anything written afterward (a new volume, a format, new files) makes recovery much harder.

Microsoft’s troubleshooting page says that when a disk goes missing or fails to initialize, “the most common reason is that the disk is failing.” A drive that held data and now shows Unknown or Not Initialized may have a damaged partition table, a bad cable, or a hardware fault. Try the cable and port checks below first. If the drive clicks, disconnects on its own, or still shows Not Initialized on another PC, and the files matter, stop using it and talk to a professional data recovery service before doing anything else.

The drive doesn’t appear in Disk Management

• Rescan. In Disk Management, select Action > Rescan Disks.
• Check the connections. For an internal drive, shut down, unplug the PC, and reseat the SATA data and power cables or the M.2 drive. Try a different SATA port or cable. For an external drive, use another USB port directly on the PC and a different cable. Microsoft notes that “cables fail often.”
• Check the firmware. Restart and open your PC’s BIOS or UEFI setup to see whether the drive is listed. If it isn’t listed there, Windows can’t see it either, and the cause is hardware or a firmware setting. Here’s how to enter BIOS or UEFI in Windows 10.
• Check Device Manager. Right-click Start, select Device Manager, and expand Disk drives. If the drive has a yellow exclamation mark, right-click it, select Uninstall device, and then select Action > Scan for hardware changes. For NVMe drives, installing the PC maker’s latest storage or chipset drivers can help.
• Try another PC. If the drive doesn’t show up there either, the drive itself is the likely problem.

Initialize Disk is grayed out or missing

• Make sure you right-clicked the gray disk label on the left, not the bar.
• If the disk is Offline, bring it Online first.
• If the disk already says Basic or Online, it’s already initialized. Go straight to Create and format a volume.
• Some USB drives can’t be initialized. Microsoft says those drives are only formatted and given a drive letter, so right-click the volume and choose Format instead.
• If none of that works, try the DiskPart method.

“Incorrect function,” “device not ready” or I/O device errors

These messages generally mean Windows couldn’t write to the disk at all. Common causes are a loose or faulty cable, a USB port or enclosure that doesn’t supply enough power, an outdated storage driver, or a failing drive. Work through the connection, Device Manager and other-PC checks above. If the error follows the drive to a second computer, the drive or its enclosure is likely faulty, and a new drive should be returned under warranty rather than repaired.

A large drive only shows about 2 TB

The disk was initialized as MBR. If it’s empty, delete the volume (right-click the bar > Delete Volume), right-click the gray disk label, select Convert to GPT Disk, and create the volume again. If you’ve already copied files to it, move them somewhere else first, because conversion in Disk Management needs an empty disk.

FAQs

Does initializing a drive erase the data on it?

Initializing rewrites the partition table rather than overwriting every file, so the old data isn’t instantly destroyed, but Windows can no longer find it. Creating a new volume and formatting it afterward, then copying new files, overwrites more of it. On SSDs, Windows may also tell the drive that the space is free, which can make recovery impossible. Treat initializing as erasing the drive.

Is initializing an SSD any different from a hard drive?

No. SATA SSDs, M.2 NVMe SSDs and spinning hard drives all use the same Initialize Disk dialog and the same wizard, and GPT with NTFS is the right default for all of them. If the new SSD is meant to replace your Windows drive rather than add storage, you’ll want to clone or move Windows 10 to the SSD instead of setting it up as an empty data drive.

Do I need to initialize a new external hard drive?

Usually not. Most external drives are formatted at the factory and work as soon as you plug them in. You’ll need to initialize one if you put a bare drive in an enclosure, or if it shows Not Initialized in Disk Management. Some portable SSDs ship formatted as exFAT; the SanDisk Extreme Portable SSD setup guide for Windows 10 shows how to check first.

How long does initializing take?

The initialization itself takes a second or two. A quick format in the New Simple Volume Wizard also finishes in seconds. If you untick quick format, Windows checks every sector, which can take hours on a large hard drive.

Can I change the drive letter or name later?

Yes. To rename the drive, right-click it in File Explorer and choose Rename. To change the letter, right-click the volume in Disk Management and choose Change Drive Letter and Paths; there’s a full walkthrough on changing a drive letter in Windows 10. Neither change affects the files on the drive.

Next step

Your new drive is ready for files. A good first job is pointing your backups or a large folder, like Pictures or a game library, at it. To see how the new disk’s space is laid out next to your other drives, you can view partitions in Windows 10.