Windows Was Unable to Complete the Format: SD Card and USB Fixes

You try to format an SD card or USB flash drive, and Windows stops with: “Windows was unable to complete the format.” You try again and get the same message. Before you go further, answer one question: is there anything on this card you need? If there is, stop trying to format it. Formatting is the wrong tool for getting files back, and the reason the format is failing may be the very thing protecting your data.

Why Windows was unable to complete the format

A format writes a new file system to the card. If Windows can’t finish writing it, one of these is usually why:

1. Write protection. Full-size SD cards and microSD adapters have a small lock switch on the side. If it’s slid down to “Lock,” the card is read-only. Windows can also be blocked from writing by a disk attribute or a policy setting.
2. The card has locked itself into read-only mode. Flash memory wears out. When a card’s controller detects that it can no longer write safely, many controllers switch the card permanently to read-only to protect what’s already stored. Writes fail, including formats, but reads often still work.
3. Bad flash memory or a failing controller. Physically damaged or worn-out memory can make writes fail partway through.
4. A badly damaged file system or partition table. Windows’ format dialog works on an existing volume. If the partition structure is damaged, the quick format through File Explorer can fail.
5. A bad card reader, adapter, or port. Cheap readers and worn adapters cause intermittent write failures.

If the card has files you need: copy first

Try to open the card and copy your files to your computer’s internal drive or another drive. If the card is in read-only mode, this often works even though formatting doesn’t.

• If you can browse the files, copy everything you need right now, before trying anything else.
• If the card shows as RAW or asks you to format it, see SD card needs formatting. Don’t format.
• If the card isn’t detected at all, see SD card not showing up.
• If you can see the card but not the files, reputable read-only recovery software can often scan it. Save recovered files to a different drive. See is data recovery software safe?

Every failed format attempt sends write commands to a card that may already be failing. Once you know there’s data you need, stop.

Fixes for a card or drive with nothing you need

Everything below writes to the card. Use these steps only once your files are copied off, or if the card is empty or the data doesn’t matter.

1. Check the lock switch and the reader

• Slide the lock switch on the SD card or adapter up, away from “Lock.” Switches can slip, so make sure it’s fully in the unlocked position.
• Try a different card reader or adapter, or a different USB port.

2. Format from Disk Management

Right-click Start > Disk Management. Find the card. It’s listed as Removable, and check the size to make sure you have the right one.

• If it has a partition, right-click it and choose Format. Pick exFAT for cards larger than 32 GB or FAT32 for 32 GB and smaller, and leave Perform a quick format checked.
• If the space shows as Unallocated, right-click it and choose New Simple Volume.

3. Clear read-only flags and rebuild with diskpart

Warning: The clean command below erases everything on the disk you select. Choosing the wrong disk number will wipe that disk instead, including your main drive or a backup drive. Unplug other external drives before you start, and check the size carefully.

Open Command Prompt as administrator and run:

diskpart
list disk
select disk 2
attributes disk

Replace 2 with the number that matches your card’s size. attributes disk shows whether Read-only is set. If it says Yes, try:

attributes disk clear readonly

Then wipe the partition table and create a fresh partition:

clean
create partition primary
format fs=exfat quick
assign
exit

Use fs=fat32 instead for cards 32 GB or smaller if your camera or device requires it.

4. Check for a write-protect policy

If every USB drive and card on this computer is write-protected, an administrator or management software may have set a policy. Check the registry at:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\StorageDevicePolicies

If a value named WriteProtect exists and is set to 1, that’s blocking writes to removable drives. On a work computer, talk to your IT department rather than changing it yourself. For more on this, see disk is write-protected.

When the card is done

If attributes disk clear readonly doesn’t stick, clean fails, or the card reverts to read-only after you unplug it, the card’s controller has locked it. There’s no software fix for that: the card has reached the end of its life. Copy anything you can, then replace the card. Don’t keep using it for new photos or video.

The same goes for a USB flash drive. If it isn’t recognized or keeps failing to format, it’s time for a new one.

The bottom line

“Windows was unable to complete the format” usually means the card or drive can’t be written to. That might be a lock switch, a read-only flag, or flash memory that has locked itself read-only as it fails. If there’s anything on it you need, stop trying to format and copy or recover your files first. Only once the data is safe should you use Disk Management or diskpart, and double-check the disk number before you clean anything.

If the card holds photos or files you can’t replace and you can’t get them off, our SD card recovery service recovers failed and read-only cards for one flat $1,200 price for a single device. Shipping is free and prepaid, and you pay nothing unless we recover your data.