Low Operating Systems ✓ Solution Verified by Community (0+ upvotes)

How to fix error error-not-ready in Windows 11

ERROR_NOT_READY = 21

65% success rate
👥 0+ users verified
📅 Updated: 2026-08-12
⏱️ 15 min read
Fix based on community reports and expert analysis. Last verified: 2026-08-12 · How we verify fixes
Error Codeerror-not-ready
Affected SystemWindows 11 (Microsoft)
DifficultyLow
Estimated Time15 min

Solution Steps

  1. 1 First, safely eject the drive and reinsert it. Click the 'Safely Remove Hardware' icon in the system tray (bottom-right corner, may be hidden behind an arrow), select your device, and wait for the 'Safe to Remove Hardware' message. Then unplug and plug it back in. This resets the connection and often fixes the 'not ready' state.
  2. 2 Try a different USB port. Plug the drive into another port, preferably directly on the motherboard (back of the PC) rather than a front panel or hub. Some ports may not provide enough power or have driver issues, causing the drive to not initialize properly.
  3. 3 Open Disk Management to check if the drive is recognized. Press Windows key + X and select 'Disk Management' from the menu. Look for your drive (it may show as 'Removable' or with a drive letter). If it appears as 'Unallocated' or 'No Media', the drive may be faulty or not inserted properly. If it shows as 'Online', right-click and select 'Change Drive Letter and Paths' to assign a new letter.
  4. 4 Update the drive's driver. Press Windows key + X and select 'Device Manager'. Expand 'Disk drives', right-click your drive, and select 'Update driver'. Choose 'Search automatically for drivers'. This ensures Windows has the latest driver, which can fix communication issues.
  5. 5 If the drive is an external HDD or SSD, check the cable and connection. Try a different cable (if possible) and ensure the connector is firmly seated. A loose or damaged cable can cause intermittent 'not ready' errors.
  6. 6 As a last resort, if the drive is new and empty, you can format it. In File Explorer, right-click the drive and select 'Format'. Choose a file system (NTFS for Windows, exFAT for compatibility) and click 'Start'. This will erase all data, so only do this if you don't need anything on it.

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