9 Fixes For “System Thread Exception Not Handled” Error

The Blue Screen of Death (BSoD) is an infuriating part of the Windows Operating System (OS). There are more than 500 BSoDs that appear on your screen due to critical errors. This article is about the System Thread Exception not Handled BSoD. If you have experienced this error before, this article also contains the necessary precautions to avoid this issue. 

What is the System Thread Exception not Handled BSoD?

The System Thread Exception not Handled Blue Screen of Death on a Windows 10 computer

If you see the SYSTEM_THREAD_EXCEPTION_NOT_HANDLED error message on a big, blue screen, it means that your system’s handler couldn’t control the exception created by a system thread. When this happens, a Blue Screen of Death is forced to be displayed with a specific stop code, while the computer attempts to figure out what went wrong. One of the biggest symptoms of this Windows 10 blue screen error is that it can put you in a never-ending boot loop.

What do the file names on the System Thread Exception not Handled error code mean?

As mentioned above, there is, usually, a stop code that is placed right after the SYSTEM_THREAD_EXCEPTION_NOT_HANDLED error message in the BSoD. However, the same error code does not appear on all computers. Each one of them has a unique meaning. In this context, all of them are corrupted system files. 

This is what the stop code on your computer means – 

  1. Atikmdag.sys

The Atikmdag.sys is the graphics card driver’s system file for computers with AMD Radeon graphics cards. If you see this code with the BSoD error message, it means that the AMD graphics drivers are old or not installed properly. 

  1. Nvlddmkm.sys

The Nvlddmkm.sys is the video card driver for Nvidia’s kernel driver on Windows computers.  

  1. Dxgmms2.sys

If you see this error message, it means that the problem lies with the DirectX drivers and their system files. 

  1. Ntfs.sys

The Ntfs.sys is the system file for the Windows NT server. There could be crashes or errors related to this file if you see this as the error code. 

  1. Bcmwl63a.sys

This system file is for the Broadcom 802.11 wireless Network Adapter driver. Though it is an unusual external element, it can cause this BSoD.

  1. CMUDA.sys

If your audio output device is connected with the help of a USB port, a unique driver is created. If this driver fails you will face this error. 

  1. Fltmgr.sys

These are the system files for the Microsoft FileSystem Filter Manager. You can see this at the end of the error message too. 

What causes the System Thread Exception not Handled issue on your Windows 10 PC?

There are not many reasons as to why the System Thread Exception not Handled BSoD is displayed on your screen. These are what can possibly cause this blue screen on a Windows 10 based computer. 

  1. A reboot or a normal boot of the system can make this error appear instead of letting you sign in to your PC. The reasons are unknown. 
  2. It can show up when a program is using the computer’s graphics card. 
  3. The GPU drivers are old or corrupt. 
  4. Graphics Card drivers have been taken over by malware or some other form of virus. 

Steps to fix the System Thread Exception not Handled error on Windows 10

  1. Launch the Windows OS in Safe Mode
    1. Windows Settings
    2. Sign-in page
    3. Blank page or crashed system
  2. Locate the troublesome driver
  3. Update drivers or Rollback to a previously installed driver software version
  4. Rename the corrupt File
  5. Run the DISM and SFC scans
  6. Restore the system with a System Restore point
  7. Perform a Memory Diagnosis test
  8. Update the UEFI/BIOS Firmware
  9. Do a Clean boot of your Windows OS
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Getting rid of the System Thread Exception not Handled error message

Launch the Windows OS in Safe Mode

Safe mode lets Windows users access only the most important features of the computer. If the problem does not exist in safe mode, it means that a driver is not responsible for it. There are three ways for Windows 10 users to boot into safe mode. 

Windows Settings

  1. Open Windows settings on your PC by pressing Windows + I keys together. You can also launch it through the Start menu (Windows key).
  2. Open the Update & Security settings tile. On the left pane, choose the Recovery tab. From the Advanced Startup section, select Restart Now
Recovery settings page in the Windows Settings
  1. Once the rebooting is done, you will see the Choose an Option screen.
  2. Select a way for the computer to boot Windows up in the Safe mode. Your system is able to boot into three types of safe mode. 
  1. Normal Safe Mode –  press the number 4 button or the F4 button on your keyboard.
  2. Safe Mode with Networking – press the 5 key or F5 key.
  3. Safe Mode with Command Prompt – press the 6 or F6 key

Sign-in page

  1. Press and hold the Shift key on the keyboard and click on the Power button on the bottom right part of the screen.
  2. Now, click on Restart and the Operating System will reboot. From the Choose an Option menu, do as instructed and choose Troubleshoot.
  3. Open the Advanced Options
  4. Click on Startup Settings. If you aren’t able to see this option, select it from the ‘See more recovery options’ menu. 
  5. Windows 10 would warn you of the changes that will happen to your computer if it was rebooted. Consider this and choose Restart.

Troubleshoot > Advanced Options > Startup Settings > Restart

  1. On the next page, select what type of Safe mode that you want your system to boot up in.

Blank page or crashed system

If your Windows 10 PC has crashed and all you see is a lit black screen, this is a symptom that your PC is currently facing a critical problem. If you need the Safe Mode here, you can launch it by pushing the power button to turn the computer off and back on. While the OS and the hard drive boot up, turn it off again. Repeat these steps thrice and this will launch the Automatic Repair window. You will now have to choose one of the types of booting up the PC in safe mode. 

Locate the troublesome driver

The following processes involve a lot of drivers and we cannot make changes without finding out which driver is responsible for the System Thread Exception not Handled issue on your computer. The Event Viewer will help you locate the driver that is faulty and has been causing trouble. 

These are the steps to find the responsible driver through the Event Viewer:

  1. Launch the Run tool through the start menu or by pressing Windows + R keys.
  2. Execute the eventvwr command and press Enter or click on the Ok button. 
  3. Navigate to the Windows logs section and open the drop-down menu in it. 
  4. Choose the system option and locate the system thread exception not handled error.

You will be able to check the details about which driver has been causing you trouble and some other details. Note the driver that causes this error.

Update drivers or Rollback to a different driver software version

The best way to deal with a driver-related issue is to update it to a newer version or to roll back to a previous version of the driver software. These are the steps to follow these procedures to fix the issue.

  1. Bring up the Quick link (Power User) menu by right-clicking on the Start button. You can also use the Windows key + X keyboard hotkeys. 
  2. Select Device Manager from it to open the window. 
  3. Now, expand the section which contains the problematic driver. If your Graphics card is causing the issue, you’ll find them in the Display Adapters section. For sound drivers, look in the Sound, Video, and Game controllers category. If your audio output comes through the USB port, check the Universal Serial Bus controllers section. 
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Device Manager window with all sets of devices available on the computer
  1. Double-click the device to open the Device Properties dialog box and go into the Driver tab. 
  2. Click on Update driver and choose Search automatically for drivers in the update wizard to update the drivers. This will download the latest version of the driver and install it for you. 
  3. To go to the previous version of the driver software, click on the Roll Back driver button. This driver will start using the previously installed version of this software.

If this doesn’t work, you can also click on the Uninstall Device option and then, download a new version of the driver from the manufacturer’s website. If you see an option named “Delete the driver software for this device”, check the box and click on the Uninstall button.

Restart your computer after this process. 

Rename the faulty driver File

When a faulty driver is causing BSoDs, you can change its name so that it will make a new copy of the driver and thereby, cause it to reinstall. This is how you can rename the corrupt file. 

  1. Open the Windows File Explorer window (Windows + E) and go to this folder directory:

C:\ Windows\ System32\ drivers

  1. Locate the faulty driver that you noticed in the Event Viewer and right-click on it.
  2. From the context menu, choose Rename
  3. Delete the format part of the name and replace it with .old.
  4. Save the changes and close the window.

After all, this is complete, you have to reboot the system to save these changes. 

Run the DISM and SFC scans

The Deployment Image Servicing and Management (DISM) is a system tool that is run to make changes in the Windows 10 installation media or to find and fix issues that can arise in the Windows image file. 

These are the steps to perform a DISM scan.

  1. Type in cmd in the search bar at the bottom of your screen and select Run as Administrator in the search results. This will launch the Command prompt window with admin privileges. 
  2. In the Command Prompt window, you have to execute the following commands in the given order:

DISM.exe /Online /Cleanup-image /Scanhealth

Scans the system for corrupted files.

DISM.exe /Online /Cleanup-image /Checkhealth

Checks if the image files are healthy or corrupt.

DISM.exe /Online /Cleanup-image /Restorehealth

Fixes the detected file damage.

Executed DISM command lines
  1. Press Enter to execute these script lines. 

A System File Checker (SFC) is a scanning tool that is used to find file damage and replace them with a fresh and compatible copy of the same file so that the computer runs without any major errors. 

These are the steps to start an SFC scan.

  1. Open the Command Prompt tool or the Windows PowerShell utility along with system administrator privileges. The search bar will be an ideal option for this.
  2. In the script window, enter this command:

sfc /scannow

Executed SFC scan command
  1. Now, press Enter on your keyboard and execute it.

We recommend running the SFC scan two or three times, just to be safe. 

Note: It is important to open the Windows PowerShell or Command Prompt as administrator of the computer, as these operations will make changes in the computer configuration. 

Restore the system with a System Restore point

  1. Insert a USB drive that contains the Windows installation media to a USB port and restart your computer. You can get the Windows Installation media source from the Microsoft website
  2. Then, launch the Troubleshoot settings and go into the Advanced Options window.
  3. Once you’re on the Advanced Options page, select the System Restore option. As an alternative, search for System Restore through the taskbar and open the topmost result.
  4. In the System Properties dialog box, press the System Restore button, from under the System Protection tab.
  5. Generate a restore point and click on the Next button in the System Restore window.
System Restore window
  1. If you have created restore points previously, you can see them and access their details. 
  2. Click on the Finish button and select Yes to close this window.

Perform a Memory Diagnosis test

Windows 10 has a built-in scanner that will exclusively check for issues that can root from the computer’s RAM. Sudden RAM crashes can also display blue screen errors. The Memory Diagnostic tool can be used to find and fix most problems with the computer’s physical memory, logically. 

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These steps will help you run a memory diagnostic test.

  1. Boot up your computer. A normal boot is acceptable but booting up in Safe mode is recommended. Refer to the above steps. 
  2. Press the Windows key and R to open the Run tool. 
  3. Open the Memory Diagnosis dialog box, by typing in the mdsched.exe command and running it with the help of the Enter key or the Ok button. 
  4. Click on the Restart now and check for problems option to begin the process. It can take quite a long time to finish. 
  5. Once the diagnosis is complete, you will be able to find the results in the Event Viewer window. 

Update the UEFI/BIOS

The UEFI/BIOS is the software that manages the events that take place during the time your computer takes to sign in to the Windows OS. Since you can experience the System Thread Exception not handled error when you boot your computer up, this fix System Thread Exception not handled error on your computer. 

  1. Go to your motherboard or laptop manufacturer’s website with the help of a browser.
  2. Here, you will have to find the latest version of the BIOS software and download it.
  3. Once the download is complete, go to the download location and run it as the Administrator. You will generally download an executable file, that can be run easily. 
  4. If you get a compressed file, you have to extract it to a USB drive, connect the USB drive to your computer, and launch BIOS menu to install the update.

This is a very risky process as it can stop the computer from functioning normally. If your system has an interface, that lets you download BIOS updates, use it. 

Do a Clean boot of your Windows OS

  1. Right-click on the Start menu and choose Run from the Quick Link menu.
  2. Click on Ok or press Enter to execute the msconfig command.
  3. In the General tab, click on the Load Startup items checkbox to disable it.
General tab in System Configuration window
  1. Then, open the Services tab and check the Hide all Microsoft services option and click on the Disable all button. 
Services tab in System Configuration window
  1. Go into the Startup tab and click on the Open Task Manager link.
  2. Open the Startup tab in the Task Manager and disable every process that is enabled in this window.
Disable option for process startup
  1. Close the Task Manager by clicking on Apply and Ok buttons.

Reboot the system after this process is complete, for a clean boot.

These are the different steps that can be used to fix System Thread Exception not Handled error on your Windows 10 computer. By now, you should have realized that though it sounds scary, it is actually nothing to worry about.

FAQs

How do I fix system thread exception not handled?

To fix the System Thread Exception not Handled error, boot into safe mode, update, roll back, or uninstall and reinstall the faulty driver, install the latest version of the BIOS software, and finally, do a clean boot of your computer. 

What does system thread not handled mean?

The SYSTEM_THREAD_EXCEPTION_NOT_HANDLED error message means that your system’s handler couldn’t control the exception created by a system thread. This could be caused by faulty drivers, or RAM issues when the system is being booted up. 

Can RAM cause system thread exception not handled?

Yes, the CPU memory or RAM plays an important part in the functioning of a computer from the moment it is booted up to the second the computer is shut down. The System Thread Exception not Handled error shows up usually when your boot your computer up. This is one of the reasons that can show you this blue screen error. 

How do I fix the system thread exception not handled Fltmgr Sys?

To fix the System Thread Exception not Handled blue screen error, you can –
Update or Rollback your drivers
Rename the corrupt file 
Perform DISM and SFC scans
Go to a saved System Restore point
Diagnose the system memory
Update your UEFI/BIOS Firmware
Perform a Clean boot of the system