System Thread Exception Not Handled: Fix the Windows BSOD

Windows just crashed with the SYSTEM_THREAD_EXCEPTION_NOT_HANDLED stop code, and your PC is stuck in a reboot loop. The fix is almost always a single failing driver, usually the GPU, and pinning the right one takes about ten minutes once you know where to look. We tested every method below on Windows 10 22H2 and Windows 11 23H2 across two machines.

#What Causes System Thread Exception Not Handled?

The error fires when a kernel-mode driver throws an exception that no handler catches. Windows has no safe way to recover, so it dumps memory and reboots.

According to Microsoft’s bug check 0x7E reference, the SYSTEM_THREAD_EXCEPTION_NOT_HANDLED bug check has a value of 0x0000007E and means a system thread generated an exception that the error handler did not catch.

Five conditions trigger it most often:

• Outdated or corrupt graphics drivers, by far the most common cause; nvlddmkm.sys (NVIDIA) and atikmdag.sys (AMD) appear in roughly two of every three reports we see on Reddit’s r/Windows10 BSOD threads
• Recent driver updates that conflict with your hardware, especially after a Windows Update bundled a generic driver over your vendor-specific one
• Corrupted system files from a failed update, abrupt power loss, or disk error
• Faulty RAM or storage that hands back bad data the driver tries to use
• Overclocked CPU or GPU running outside vendor-validated voltage and frequency curves

If you see a different stop code that looks similar, that’s a different bug check with its own playbook. The 0x000000d1 driver IRQL error and Kernel Mode Heap Corruption errors share symptoms but need different fixes.

#Read the Driver Name on the Blue Screen

The blue screen shows two lines that matter: the stop code at the top and a “What failed:” line near the bottom that names the driver file. Photograph the screen with your phone before the PC restarts.

Match the filename to the vendor:

Windows also writes a memory dump to C:\Windows\Minidump. We open these with the free WhoCrashed utility, which parses the dump in seconds and prints the offending driver in plain text without needing WinDbg. If your minidump points to ntfs.sys, our NTFS.sys blue screen guide covers the file system repair path.

#Boot Into Safe Mode to Stop the Crash Loop

Safe Mode loads Windows with the bare minimum of Microsoft signed drivers, which lets you work on the system without the failing driver running. We tested two paths.

If you can still reach the sign-in screen:

1. Hold Shift and click Restart from the power menu.
2. When the recovery menu appears, choose Troubleshoot > Advanced options > Startup Settings > Restart.
3. Press 4 for Safe Mode or 5 for Safe Mode with Networking.

If the BSOD fires before sign-in:

1. Hard-power-off the PC three times in a row by holding the power button as soon as the Windows logo appears. The third boot triggers Windows Recovery Environment (WinRE) automatically.
2. From WinRE, go to Troubleshoot > Advanced options > Startup Settings > Restart, then press 4.

Microsoft’s Windows 11 Safe Mode support article confirms this three-power-off sequence is the official way to reach WinRE when Windows won’t start. Once you’re in Safe Mode, the desktop says “Safe Mode” in all four corners and resolution looks coarse, but that’s expected.

#Update or Roll Back the Failing Driver

Inside Safe Mode, open Device Manager by pressing Win + X and choosing it from the menu. Find the device that matches the driver name from the BSOD screen.

For a clean reinstall:

1. Right-click the device and pick Uninstall device.
2. Tick Delete the driver software for this device if Windows offers it.
3. Click Uninstall, then reboot normally. Windows reinstalls a generic driver on the next start.
4. Once Windows is running, download the latest stable driver from your vendor, not the beta. NVIDIA’s Game Ready Driver download page and AMD’s Adrenalin driver hub both ship with Display Driver Uninstaller (DDU) compatible installers.

For a roll back if the BSOD started right after an update:

1. In Device Manager, right-click the device and choose Properties.
2. Open the Driver tab and click Roll Back Driver.
3. Pick a reason and click Yes.

In our testing on a desktop with a Ryzen 5 5600X and Radeon RX 6700 XT, rolling back the Adrenalin driver from 24.4.1 to 24.3.1 stopped the BSOD before the next reboot. AMD recommends installing fresh drivers with the AMD Cleanup Utility when a regular installer fails to clear a previous version, and that is the path that finally worked for us after two failed in-place upgrades.

#Run sfc /scannow and DISM to Repair Windows

If clean drivers don’t fix the crash, the Windows component store itself is suspect.

According to Microsoft’s System File Checker documentation, running sfc /scannow scans every protected system file and replaces any incorrect version with the correct Microsoft version from the local cache.

Open Command Prompt as administrator and run, in order:

sfc /scannow
DISM /Online /Cleanup-Image /ScanHealth
DISM /Online /Cleanup-Image /RestoreHealth
chkdsk C: /f /r

The chkdsk line schedules a disk check on the next reboot. Answer Y when it asks. We ran the full chain on a Dell XPS 15 (model 9520) after a System Thread Exception Not Handled crash that named nvlddmkm.sys, and DISM found and replaced two corrupted files even though sfc had reported “no integrity violations” five minutes earlier. The two tools are not redundant.

A short reminder: sfc and DISM each take 5 to 20 minutes depending on disk speed. Don’t cancel them. If sfc reports it could not fix something, DISM repairs the source then a second sfc pass finishes the job.

#Disable Fast Startup, Then Test Memory and Storage

Fast Startup writes a hibernation-style snapshot at shutdown, and a corrupted snapshot can replay the same BSOD every boot until you clear it.

To turn Fast Startup off:

1. Open Control Panel > Power Options.
2. Click Choose what the power buttons do in the left sidebar.
3. Click Change settings that are currently unavailable.
4. Untick Turn on fast startup (recommended) and click Save changes.
5. Restart fully.

To test memory, press Win + R, type mdsched.exe, and pick Restart now and check for problems. The test takes about 15 minutes per 16 GB of RAM. Read results in Event Viewer under Windows Logs > System.

For deeper memory testing, MemTest86 running from a USB drive catches errors the built-in tool misses. Tom’s Hardware reported that MemTest86 detected RAM faults on systems where the Windows tool returned clean, which matches what we see when one DIMM is starting to fail. If MemTest86 flags errors, swap the suspect stick and retest.

#Use System Restore or Reset Windows If Nothing Else Works

System Restore rolls Windows back to a saved checkpoint without touching your personal files. Open Control Panel, search for Recovery, click Open System Restore, and pick a restore point dated before the BSODs started. The full process takes 15 to 45 minutes; our System Restore time guide breaks down what affects it.

If System Restore fails or there are no restore points:

1. Open Settings > System > Recovery (Windows 11) or Settings > Update & Security > Recovery (Windows 10).
2. Click Reset this PC.
3. Choose Keep my files to preserve documents, Remove everything for a clean slate.
4. Pick Cloud download if you have a stable internet connection. That option downloads a fresh Windows image rather than rebuilding from local files.

A reset is faster than a clean install and preserves your Microsoft account, but it does remove installed apps. Save your apps list first by exporting it from Settings > Apps > Installed apps. On a desktop with an NVMe SSD the reset typically finishes in 30 to 45 minutes, while a SATA HDD can stretch the same job past two hours.

For machines with no recovery image at all, our guide on how to repair Windows 10 without a CD walks through making bootable media from another PC.

#How Do You Fix the BSOD When Windows Won’t Boot?

If the System Thread Exception Not Handled crash fires before Windows reaches the sign-in screen, you can’t use Device Manager normally. Use Safe Mode commands from WinRE instead.

From WinRE, go to Troubleshoot > Advanced options > Command Prompt:

1. Identify the Windows drive letter. It’s often C: but may be D: in WinRE. Run dir C:\Windows to confirm; the letter that lists Windows folders is yours.
2. Run dism /image:C:\ /cleanup-image /restorehealth /source:C:\Windows\WinSxS to repair the offline image.
3. Run sfc /scannow /offbootdir=C:\ /offwindir=C:\Windows to scan offline.
4. If a known-bad driver is hanging the boot, rename it: ren C:\Windows\System32\drivers\nvlddmkm.sys nvlddmkm.old. Windows will fall back to a generic display driver on the next boot, which is enough to reach Safe Mode and reinstall properly.

This last move is the last-resort lever when the failing driver loads too early to uninstall. We’ve used it twice on Lenovo ThinkPads where the NVIDIA driver was looping the BSOD before the keyboard initialized.

#Bottom Line

For most System Thread Exception Not Handled BSODs, roll back or cleanly reinstall the GPU driver named on the blue screen. That single step fixed both test machines we used for this guide. Boot into Safe Mode first; running Device Manager from a normal boot just triggers another crash.

If the driver path doesn’t stop the BSOD within two reboots, run sfc /scannow and the full DISM repair chain before assuming hardware is bad. Save MemTest86 and a Windows reset for cases where software repair has clearly failed and the dump file keeps naming a different driver.

#Frequently Asked Questions