The Problem

SYSTEM_THREAD_EXCEPTION_NOT_HANDLED (stop code 0x0000007E) means a kernel thread — almost always one belonging to a driver — hit an error it had no handler for. Windows cannot let a driver continue in an unknown state, so it stops the machine.

The important detail people miss: this stop code is usually generous enough to name the culprit. Look at the line under the message. If it reads SYSTEM_THREAD_EXCEPTION_NOT_HANDLED (nvlddmkm.sys) or (bcmwl63a.sys), you already know which driver to fix, and you can skip most of the guesswork below.

No file named on the screen? The minidump still records it — Step 1 shows how to read it. Getting a different stop code every time? That pattern points at RAM or power instead; start with how to fix a BSOD.

Symptoms

Blue screen reading SYSTEM_THREAD_EXCEPTION_NOT_HANDLED, often with a .sys filename in brackets.
Crashes cluster around one activity — launching a game, joining a video call, connecting to Wi-Fi, plugging in a device.
The PC reboots into the same crash repeatedly, sometimes before you reach the desktop.
Started shortly after a driver update, a Windows update, or new hardware.

Step 1: Get the Name of the Failing Driver

Photograph the blue screen and read the text in brackets after the stop code.
If nothing is named, press Windows + R, type eventvwr.msc, press Enter.
Go to Windows Logs → System, filter by source BugCheck, and open the most recent entry.
Minidumps are written to C:\Windows\Minidump. If the folder is empty, enable them: Windows + R → sysdm.cpl → Advanced → Startup and Recovery → Settings → set Write debugging information to Small memory dump (256 KB), then wait for the next crash.
Full walkthrough: how to use Event Viewer to find why your PC crashed.

Common names and what they belong to:

| File | Owner | |---|---| | nvlddmkm.sys | NVIDIA graphics | | atikmdag.sys / amdkmdag.sys | AMD graphics | | igdkmd64.sys | Intel integrated graphics | | bcmwl63a.sys, netwtw*.sys | Wi-Fi adapter | | ntfs.sys, storahci.sys | Storage / file system | | dxgkrnl.sys | DirectX graphics kernel |

Step 2: Get In Using Safe Mode If the PC Keeps Looping

If Windows crashes before you can do anything useful, you need Safe Mode — it loads Microsoft's basic drivers only, which usually sidesteps the crash entirely.

Force three failed boots (power off with the button as Windows starts loading) to trigger the recovery screen.
Choose Troubleshoot → Advanced options → Startup Settings → Restart, then press 4.
Everything from Step 3 onward can be done from Safe Mode.
Detailed routes in: how to enter Safe Mode in Windows 11.

Step 3: Roll Back or Reinstall the Named Driver

Right-click Start → Device Manager.
Find the device matching the .sys file from Step 1 (graphics under Display adapters, Wi-Fi under Network adapters).
Right-click → Properties → Driver tab.
If Roll Back Driver is available, use it — that means a previous version is still on the machine and the crash likely started with the update. Reboot and test.
If it is greyed out, choose Uninstall device, tick Attempt to remove the driver for this device, reboot, then install the current version from the hardware vendor's own support page — not from a driver-download site.
General method: how to update outdated drivers.

Step 4: Do a Clean Graphics Driver Install

If the named file is a graphics driver, a normal reinstall often leaves the broken files behind. Strip it properly.

Download the correct driver package from NVIDIA, AMD, or Intel first — you will be without graphics drivers for a few minutes.
Run Display Driver Uninstaller in Safe Mode to remove every trace of the old driver.
Reboot, install the fresh package, and decline any optional extras you do not use.
Step-by-step: clean install GPU drivers with DDU.
If the screen misbehaves rather than crashing outright, see fix display driver stopped responding.

Step 5: Repair Damaged System Files

A corrupt system file can make a perfectly good driver fail.

Right-click Start → Terminal (Admin).
Run:
```
sfc /scannow
```

Then:

DISM /Online /Cleanup-Image /RestoreHealth

Reboot and run sfc /scannow once more — DISM repairs the component store that SFC pulls replacements from, so the second pass often fixes what the first could not.
Full guide: how to run SFC and DISM.

Step 6: Use Driver Verifier When Nothing Is Named

Driver Verifier deliberately stresses third-party drivers until the guilty one fails and gets named in the dump. Only do this once you have working backups and know how to reach Safe Mode, because it makes the PC crash more while it runs.

Windows + R → verifier → Create custom settings (for code developers).
Tick Standard settings, then choose Automatically select unsigned drivers and Select driver names from a list — verify only non-Microsoft drivers.
Reboot and use the PC normally. The next blue screen should name a specific .sys file.
Turn it off afterwards from Terminal (Admin), or the machine stays unstable:
```
verifier /reset
```
If the PC will not boot with Verifier on, enter Safe Mode and run verifier /reset there.

Step 7: Test the Memory

Bad RAM produces exception faults in whatever driver happens to be running, so the named file can change between crashes.

Windows + R → mdsched.exe → Restart now and check for problems.
Press F1 during the test and set Test Mix to Extended.
For a trustworthy result, run MemTest86 from a USB stick for four passes or more.
Any error at all means bad memory or an unstable memory profile — test one stick at a time and leave XMP / EXPO off while testing.
Related: check and upgrade your RAM and fix MEMORY_MANAGEMENT BSOD.

Step 8: Undo the Change That Started It

Windows + R → rstrui → pick a restore point dated before the crashes began.
If the crashes started after a Windows update, remove it: Settings → Windows Update → Update history → Uninstall updates.
Full rollback method: fix Windows 11 after a bad update.
Make restore points routine afterwards: create a system restore point.

What Not to Do

Don't install drivers from third-party "driver updater" sites. Mismatched packages are a leading cause of this exact stop code.
Don't leave Driver Verifier running once it has named a file — it is a diagnostic, not a fix, and it degrades stability.
Don't jump straight to reinstalling Windows. If a failing RAM stick or a vendor driver is the cause, a clean install crashes again within days.
Don't ignore a .sys name because you don't recognise it. Search the exact filename — it identifies the device every time.

Still Not Working?

If crashes persist with clean drivers, repaired system files, tested memory, and current firmware, look at heat and power next: fix CPU overheating and thermal throttling. Back your data up before going further — set up automatic backups.

Fix SYSTEM_THREAD_EXCEPTION_NOT_HANDLED in Windows 11