Windows BSOD Error 0x00000066 — CACHE_INITIALIZATION_FAILED Fix

What Does This Error Mean?

The 0x00000066 blue screen means the Windows Cache Manager failed to initialize at startup. The Cache Manager is the part of Windows that stores recently used files in RAM so your system runs faster. When it cannot start properly, Windows crashes rather than risk data loss. This error is commonly caused by faulty RAM, a failing hard drive, or corrupted Windows system files.

Affected Models

Windows 10
Windows 11
Windows 8.1
Windows Server 2019

Common Causes

One or more RAM modules are faulty, causing the Cache Manager to fail when allocating memory at startup
The hard drive or SSD has developed bad sectors that interfere with reading system files during boot
Core Windows system files related to the Cache Manager have become corrupted
A recently installed driver or software is conflicting with Windows memory management at startup
An overclocked processor or RAM is operating outside of stable parameters and causing random crashes

How to Fix It

Run Windows Memory Diagnostic to check your RAM. Type 'Windows Memory Diagnostic' in the Start menu and choose 'Restart now and check for problems.'

The test runs before Windows loads and takes about 15 to 20 minutes. If it finds errors, your RAM needs to be replaced.
Run Check Disk to scan your hard drive for errors. Open Command Prompt as Administrator and type: chkdsk C: /f /r — then press Enter and type Y to schedule it for the next restart.

The scan runs on next boot and can take 1 to 3 hours. Bad sectors found here can explain the cache failure.
Run the System File Checker to fix corrupted Windows files. Open Command Prompt as Administrator and type: sfc /scannow

This replaces any damaged Windows system files with clean copies. Run it after Check Disk has completed.
If your computer is overclocked, enter your BIOS/UEFI and reset all settings to default. Overclocking RAM or CPU beyond stable limits commonly causes crashes like this.

Look for a 'Load Optimized Defaults' or 'Reset to Default' option in your BIOS settings.
If none of the above helps, boot from a Windows installation USB and choose 'Repair your computer' > 'Startup Repair.' This can fix boot-level issues that normal tools cannot reach.

You can download the Windows installation tool from Microsoft's website for free. You will need a USB drive of at least 8 GB.

When to Call a Professional

If memory diagnostics show hardware errors, you will need to replace the faulty RAM. If the hard drive has significant bad sectors, replacing the drive before it fails completely is important — a technician can migrate your data. If overclocking is suspected, a technician can reset your system to factory clock speeds safely.

Frequently Asked Questions

What does the Cache Manager do in Windows?

The Cache Manager is a background component of Windows that stores frequently used file data in RAM. This makes opening files and running programs faster because Windows reads from RAM instead of the much slower hard drive. When it cannot initialize, Windows has no safe way to manage this memory and must crash.

Could a power outage cause this error?

Yes. A sudden power loss while Windows was writing files can corrupt system files including those needed by the Cache Manager. Running sfc /scannow and Check Disk after a power outage is always a good idea. Using a UPS (uninterruptible power supply) can protect your computer from future power-related corruption.

Is this error related to web browser cache?

No. The Windows Cache Manager is completely separate from your browser's cache. Clearing your browser history has no effect on this error. The Cache Manager works deep inside Windows and handles system-level file caching, not web data.