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How to Fix SYSTEM_THREAD_EXCEPTION_NOT_HANDLED BSOD

8 min read
Updated: November 2026
Kernel Stop Codes

The SYSTEM_THREAD_EXCEPTION_NOT_HANDLED blue screen (BugCheck 0x0000007E) is one of the most common Windows crash errors. It indicates that a system thread running inside a third-party kernel driver generated an unhandled exception that the error handler failed to catch. Here is how to isolate the exact driver file causing it.

Step 1: Check the "What Failed:" Driver File

On modern Windows 11 and Windows 10 blue screen screens, look at the bottom line labeled "What failed:". Common examples include:

  • nvlddmkm.sys: NVIDIA Display Driver
  • amdkmdag.sys: AMD Radeon Graphics Driver
  • rtwlanu.sys: Realtek USB Wi-Fi Adapter Driver
  • epfw.sys: Third-party Antivirus Firewall filter driver

Step 2: If the Screen Reboots Too Fast, Use Event Viewer

If your PC reboots before you can read the blue screen:

  1. Open Event Viewer (Win + R > eventvwr.msc).
  2. Navigate to Windows Logs > System.
  3. Look for Event ID 1001 (BugCheck).
  4. Inspect Parameter 1: An exception code of 0xC0000005 means an Access Violation occurred in a kernel driver.

Step 3: Boot into Safe Mode with Networking

If your computer is caught in an infinite BSOD boot loop:

  1. Power on your PC. As soon as the Windows logo appears, hold down the power button for 5 seconds to force power off. Repeat this twice.
  2. Windows will launch the Automatic Repair (WinRE) blue screen.
  3. Select Advanced options > Troubleshoot > Advanced options > Startup Settings > Restart.
  4. Press 5 or F5 for Safe Mode with Networking.

Step 4: Clean Install the Offending Driver (DDU)

If the crash points to a graphics driver (nvlddmkm.sys or amdkmdag.sys), simply updating over the old driver often fails to purge corrupted registry references:

  1. In Safe Mode, run Display Driver Uninstaller (DDU) to wipe all residual GPU driver registries.
  2. Reboot into normal Windows mode.
  3. Install the clean, certified WHQL driver directly from NVIDIA or AMD's official support portal.

Step 5: Verify System Integrity and RAM

Corrupted RAM can cause random drivers to throw 0x7E exceptions. Run the native Windows memory test:

Run Shortcut
mdsched.exe