What SYSTEM_THREAD_EXCEPTION_NOT_HANDLED means

A system thread generated an exception that no handler caught. The blue screen frequently names a driver file. Display drivers such as nvlddmkm.sys (NVIDIA) or amdkmdag.sys (AMD) appear often, but the file shows which code crashed and not always why, so use it as a starting point rather than a verdict.

Common causes

  • Outdated, corrupt or incompatible drivers
  • A graphics driver conflict, for example after swapping the GPU
  • Corrupted system files
  • BIOS or firmware that needs an update

How to fix SYSTEM_THREAD_EXCEPTION_NOT_HANDLED

Work through these in order and test after each one. Stopping as soon as the crashes stop tells you which change mattered.

  1. Note the file name on the blue screen. If the screen shows a line such as "What failed" followed by a .sys file, write it down. Searching that file name shows which driver it belongs to, which tells you what to update or remove. The named file is the code that crashed, which is not always the root cause.
  2. If a display driver was named, reinstall it cleanly. Download the latest driver for your exact GPU from NVIDIA, AMD or Intel (or the laptop maker for notebooks), then install it using the vendor's clean-install option. If the newest driver is the one that started the crashes, install the previous release instead.
  3. Update the BIOS and chipset drivers. Check the motherboard or laptop maker's support page for a newer BIOS and chipset package. Read the release notes first and keep the PC on stable power during a BIOS update.
  4. Repair Windows system files. Open Terminal (Admin) and run sfc /scannow. If it reports damage it could not repair, run DISM /Online /Cleanup-Image /RestoreHealth, restart, and run sfc /scannow once more.
  5. Start in Safe Mode if Windows will not load. Hold Shift while choosing Restart, or let Windows fail to start three times to open the recovery menu. Choose Troubleshoot, Advanced options, Startup Settings, Restart, then Safe Mode. If Windows is stable there, a driver or startup program is the likely cause.
When to stop and protect your data

A different driver file named on each crash suggests a shared cause such as memory or power rather than several separate driver bugs.

Not sure this is your code?

The stop code appears as text on the blue screen. If the PC restarted before you could read it, open Event Viewer, then Windows Logs, then System, and look for a BugCheck event with ID 1001. You can also search all stop codes.

Related guides

Other driver errors