Write Protect Error
Microsoft MS-DOS PC
Severity: MinorWhat Does This Error Mean?
Write Protect Error means DOS tried to write to a floppy disk that has its write-protect tab enabled. Slide the tab to uncover the hole on a 3.5" disk, or remove the tape/sticker covering the notch on a 5.25" disk.
Affected Models
- IBM PC
- IBM XT
- IBM AT
- Compaq
- Any MS-DOS PC with floppy drive
- DOSBox emulator
Common Causes
- 3.5" floppy: write-protect tab slid open (exposing the square hole)
- 5.25" floppy: write-protect notch covered with tape or sticker
- Drive door not fully closed
- Trying to write to a commercially pressed read-only disk
- SUBST or ASSIGN command making a drive appear write-protected
How to Fix It
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Check the write-protect tab on the floppy disk.
3.5" disk: the small plastic tab at the top corner. If the square hole is OPEN (you can see through it), the disk IS write-protected. Slide the tab to COVER the hole to allow writing.
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For 5.25" disks: check the notch on the side.
If a sticker or tape covers the notch, the disk is write-protected. Peel off the sticker to allow writing.
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If you WANT the disk to be writable, check it's not a pressed (commercial) disk.
Commercial software disks are often manufactured without a write-notch at all. These cannot be made writable — copy the files to a blank disk instead.
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If protecting important data: write-protect is your friend.
Write-protecting important floppies (backups, master copies) prevents accidental deletion. Leave the tab open on anything you want to preserve.
Frequently Asked Questions
Why is write-protect backwards on 3.5" disks?
Counterintuitive but true — on 3.5" disks, the hole open = write protected, hole covered = writable. This is the opposite of 5.25" disks, where covering the notch = protected. The logic is the same (blocking the sensor), just the physical mechanism differs.