How to fix it

BAD_SYSTEM_CONFIG_INFO is a blue screen that means Windows started but couldn't read a critical registry hive — most often the SYSTEM or SECURITY hive under C:\Windows\System32\config. Without it, the kernel can't complete startup, so it stops. The classic trigger is a bad Windows Update or a botched registry edit that left the hive missing or corrupt.

What it means

Windows stores its core configuration in the registry, split into several files ("hives") on disk. At boot it loads the SYSTEM and SECURITY hives. If one of those files is missing, truncated, or corrupt, you get BAD_SYSTEM_CONFIG_INFO. The screen is telling you the configuration is the problem, not a single app.

Where you'll usually see it

  • Right after a failed or interrupted Windows Update
  • After a registry edit or a tool that touched the registry
  • After a sudden power loss while the registry was being written
  • After restoring a partial image of Windows

Common causes

  • A missing or corrupt SYSTEM or SECURITY hive file
  • A bad update that damaged the registry during install
  • A registry editor or third-party tool that truncated a hive
  • An interrupted write (power loss) during an update

Quick fixes (try these first)

  1. Last Known Good Configuration. At startup, before login, press the power button to force a shutdown, then power on and repeatedly tap F8 (or use Settings → Recovery → Advanced startup → Startup Settings → option 1) to get Last Known Good Configuration. This loads the registry backup from the last clean boot.
  2. Boot into Safe Mode. If LKGC isn't available, try Safe Mode — it loads a minimal set of hives and may let you repair.

Detailed fixes

Use a restore point. Boot into the Windows Recovery Environment (hold Shift while clicking Restart, or boot from a Windows USB → Repair your computer → Troubleshoot → Advanced options → System Restore). Pick a restore point from before the problem. This rolls the registry back to a known-good state and is the cleanest fix.

What System Restore does: it restores the registry, installed programs, and system files to a previous point without touching your personal files (documents, photos, etc.). It is the recommended first serious repair.

Recover a hive from a backup. If you have a backup of C:\Windows\System32\config\SYSTEM (and SECURITY) from before the failure, boot from a Windows USB into the Command Prompt and copy the known-good files back over the damaged ones. The config folder is where the hives live on disk.

Before doing this: the config folder is protected. You'll typically need to take ownership and grant yourself write access, or run the copy from an elevated recovery prompt. Replacing a hive is a surgical fix — if you're not comfortable doing it, prefer System Restore or a repair install over hand-editing hives.

Repair install (in-place upgrade). If you can't recover the hives, the reliable fix is to rerun Windows setup (Media Creation Tool) and choose Keep personal files and apps. This rebuilds the registry and system files while preserving your data and programs. Back up first, always.

When to suspect hardware

If the hive files keep going missing and you also see disk I/O errors or the drive is old, a failing drive can corrupt the registry files during writes. Check SMART health and consider replacing the drive. A registry that keeps "breaking" with no bad update nearby is often a disk problem in disguise.

Related errors

  • CRITICAL_PROCESS_DIED — a core process stopped
  • 0xC000021A — system process terminated
  • 0x800f081f — Windows Update source files missing