ErrorFindly
0x00000021BSODCritical

0x00000021 — Quota Underflow | Blue Screen Fix Guide

QUOTA_UNDERFLOW

Windows XPWindows VistaWindows 7Windows 8Windows 10Windows 11

What Does 0x00000021 Mean?

A process's memory quota was decremented below zero, indicating a quota tracking error.

Real-World Causes

  1. 1Driver quota management bug
  2. 2Memory corruption
  3. 3Internal kernel error

Symptoms

  • ⚠Blue screen with stop code QUOTA_UNDERFLOW
  • ⚠System reboots unexpectedly
  • ⚠Possible data loss from unsaved work

DIY Fix

Beginner-friendly steps you can try at home

  1. 1Restart your computer
  2. 2Run System File Checker (sfc /scannow)
  3. 3Check Windows Update
  4. 4Run DISM /Online /Cleanup-Image /RestoreHealth

Advanced Fix

For experienced users and IT professionals

  1. 1Analyze minidump with WinDbg
  2. 2Check Event Viewer for correlated errors
  3. 3Use Process Monitor to trace system activity
  4. 4Perform clean boot to isolate the cause

Frequently Asked Questions

What causes QUOTA_UNDERFLOW?
A process's memory quota was decremented below zero, indicating a quota tracking error.
Can I fix Quota Underflow myself?
In many cases yes. Start with basic troubleshooting like restarting, updating drivers, and running System File Checker. If the issue persists, advanced analysis of crash dumps may be needed.

Related Error Codes

0x0000001AMemory Management0x00000019Bad Pool Header

About the Author

Windows Troubleshooting Team

Verified against official Microsoft documentation and real-world diagnostic data. Error behavior confirmed across Windows 10, Windows 11, and Windows Server.