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USB drive “write-protected” and “file too large”: how to fix it

Windows won’t let you copy to your USB flash drive and says the disk is write-protected? Or it says the file is too large, even though there’s plenty of space left? Here are the causes of each error and how to fix them without losing your files.

By TECHNOARTH Editorial Team Published 2 min read

These are two different errors, with different causes. Find yours below.

In this article
  1. “The disk is write-protected”
    1. Clear the read-only flag (diskpart)
  2. “The file is too large for the destination file system”
  3. Other common errors
  4. FAQ

“The disk is write-protected”

Windows error when copying to a USB drive: the disk is write-protected
This message (1) appears when the drive’s lock switch is on, it’s marked read-only, or it’s starting to fail.

Try these in order:

  1. Physical switch: some USB drives and SD cards have a small lock switch on the side (“Lock”). Slide it the other way and plug the drive in again.
  2. Another port and another PC: if it works on another computer, the problem is a setting in your Windows (next section).
  3. Antivirus and company policies: on work computers, IT may block writing to USB drives on purpose. In that case, talk to your IT team.

Clear the read-only flag (diskpart)

  1. Open Terminal (Admin) from the Windows + X menu.
  2. Type diskpart, then list disk, and identify the USB drive by its size.
  3. Type select disk N (replace N with the USB drive’s number) and then attributes disk clear readonly.
Command Prompt with diskpart listing the USB drive as Disk 1 and attributes disk clear readonly completed
Check by its size which disk is the USB drive (1) before selecting it. The command (2) removes the read-only flag.

If nothing works: USB drives that are starting to fail switch themselves into read-only mode to protect the data. Copy your files to your PC while you can still read them and replace the drive.

“The file is too large for the destination file system”

Windows warning: the file is too large for the destination file system
This warning (1) is almost always FAT32’s 4 GB per-file limit, not a lack of space.

It’s not a lack of space. USB drives usually come formatted as FAT32, which doesn’t accept files larger than 4 GB (long videos, ISO images, backups).

Solution: format the drive as exFAT, which accepts large files and works on Windows, Mac, and many TVs and game consoles.

  1. Copy everything on the USB drive first: formatting erases everything.
  2. In File Explorer, right-click the USB drive › Format.
  3. Under File system, choose exFAT and click Start.
Format window for the USB drive with the exFAT file system selected
Choose exFAT (1) to copy files larger than 4 GB and use the drive on Windows, Mac and TVs. Formatting erases everything.

Other common errors

  • “Please insert a disk into drive” or a USB drive that shows 0 bytes: this is usually a failure of the drive’s controller. Try another PC; if it still won’t open, the data can only be recovered by a specialized company.
  • The USB drive doesn’t show up in Windows: see USB device not recognized.
  • Deleted files by accident: see recover deleted files.

FAQ

Does formatting as exFAT make the USB drive slower?

Not noticeably. Speed depends on the drive itself and the USB port.

Can I put a password on a USB drive?

On Windows Pro, with BitLocker To Go. Also see how to password-protect files and folders.

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TECHNOARTH Editorial Team

The TECHNOARTH newsroom: technology tutorials, guides, comparisons and news produced with AI assistance and checked against manufacturers’ official sources.

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