Quick answer: Check the System event log for the exact blocked driver, then either update the driver to a signed version or add an exception in Memory Integrity / Vulnerable Driver Blocklist settings.
That error code—0x000004FB—pops up when Windows refuses to load a kernel-mode driver. I know it's infuriating because the message gives you almost nothing: "This driver has been blocked from loading." No driver name, no hint why. It usually happens after a Windows feature update, a driver update gone sideways, or when third-party security software installs an old filter driver. The real culprit is often Windows' Memory Integrity (HVCI) or the Vulnerable Driver Blocklist, both designed to stop known-bad drivers—but they sometimes flag legitimate ones.
Fix 1: Identify the Blocked Driver in Event Viewer
Before you can fix it, you need to know which driver is blocked. The error dialog doesn't tell you, but Event Viewer does. This is the step most people skip, and then they end up disabling everything and breaking their system.
- Press Win + R, type
eventvwr.msc, hit Enter. - Go to Windows Logs > System.
- Look for the most recent Error or Warning event with source Kernel-PnP or CodeIntegrity.
- Click it and read the General tab. It'll name the driver file, like
olddriver.sys.
Note the driver name. If you can't find it, search the event log for "blocked" or the error code.
Fix 2: Update or Replace the Driver
If the driver is from a known vendor (e.g., a printer, GPU, or storage controller), the easiest fix is to get a newer, Microsoft-signed version.
- Open Device Manager (
devmgmt.msc). - Find the device that uses that driver. Usually it's under Storage controllers, System devices, or Printers.
- Right-click it, select Update driver, then Search automatically for drivers.
- If no update found, go to the manufacturer's site and download the latest driver for your exact Windows version.
Sometimes the driver is old but still works fine—like for an older RAID controller. In that case, you might need to disable the blocklist.
Fix 3: Allow the Driver Through Memory Integrity or Blocklist
If updating isn't possible, you can add an exception. Note: This only works if the driver is unsigned or on Microsoft's vulnerable list—you're overriding a security feature, so do this only if you trust the driver.
- Go to Start > Windows Security > Device security > Core isolation details.
- Turn off Memory integrity temporarily and reboot. If the error goes away, the driver was blocked by HVCI.
- Alternatively, in Windows Security > Device security > Kernel isolation, turn off the Microsoft Vulnerable Driver Blocklist.
If you turn off Memory Integrity, your PC will run fine but lose some protection. I'd rather you update the driver, but if it's a dead product, this is your only route.
Alternative Fix: Use the Registry to Force Load
For advanced users who know exactly what they're doing, you can add the driver to the AllowList in the registry. This is risky and can leave your system unstable, but it's a last resort.
reg add "HKLM\SYSTEM\CurrentControlSet\Control\CI" /v VulnerableDriverAllowlist /t REG_MULTI_SZ /d "C:\Windows\System32\drivers\olddriver.sys" /fReboot and test. If that doesn't work, you might be out of luck—some drivers are just too old for Windows 10 2004+.
Prevention: Keep Drivers Signed and Current
The best way to avoid this error is to never let it happen. I learned this the hard way when an old scanner driver got blocked after an update, and I spent a weekend untangling it. Now I follow these habits:
- Uninstall any driver software you don't use anymore—especially older printer or scanner utilities.
- Check Windows Update for driver updates regularly, but don't blindly install them. Read the release notes.
- Before you upgrade to a new Windows feature version, check your hardware vendor's site for driver compatibility.
If you ever see this error again, run through the Event Viewer step first. That'll save you from guessing and breaking something else.