Read the driver name under “What failed” (e.g. nvlddmkm.sys = NVIDIA, atikmdag.sys = AMD, igdkmd64.sys = Intel graphics). Boot into Safe Mode, roll back or cleanly reinstall that driver, then restart normally.

What SYSTEM_THREAD_EXCEPTION_NOT_HANDLED actually means

SYSTEM_THREAD_EXCEPTION_NOT_HANDLED means one of the threads Windows runs for itself raised an exception, such as an invalid memory access, that nothing handled. The thread is often running driver code, so the driver named on the screen is your best lead.

If the PC crashes during startup, use Safe Mode. It loads only basic drivers, so you can remove the faulty one.

Symptoms

  • Blue screen: “Stop code: SYSTEM_THREAD_EXCEPTION_NOT_HANDLED”, sometimes with a .sys file named.
  • Boot loop or crash shortly after signing in.
  • Often follows a graphics driver or Windows update.

What causes SYSTEM_THREAD_EXCEPTION_NOT_HANDLED

  • Faulty or incompatible graphics driver (most common).
  • Network, audio or storage driver bugs.
  • Corrupted system files.
  • Less often, unstable hardware or overclocking.

Try these fixes

  1. Boot into Safe Mode if neededIf Windows won't stay up long enough, hold Shift while clicking Restart (or let it fail to boot three times) and choose Troubleshoot → Advanced options → Startup Settings → Restart → 4 for Safe Mode.
  2. Fix the named driverIn Device Manager roll back the driver, or uninstall the device (tick Attempt to remove the driver) and install the latest stable version from the manufacturer. For graphics, the vendor's clean-install option helps.
  3. Undo a recent Windows updateSettings → Windows Update → Update history → Uninstall updates, if crashes started right after one.
  4. Repair system filesRepair system files with DISM, then SFC (commands below).
  5. Reset overclockingLoad default settings in the BIOS/UEFI and remove GPU tuning tools.
  6. Read the dump if no driver is shownThe crash leaves a dump file in C:\Windows\Minidump. Open it with WinDbg (!analyze -v) or BlueScreenView, and note the .sys file listed as the probable cause.

Command

DISM /Online /Cleanup-Image /RestoreHealth
sfc /scannow

Run in an elevated Command Prompt (Run as administrator). DISM can take 10–20 minutes; run sfc after it finishes, then restart.

Check it's fixed: Windows starts and runs normally outside Safe Mode for several days.

Avoiding it in future

Install graphics drivers from NVIDIA, AMD or Intel directly and avoid beta drivers on work machines.