The “System Thread Exception Not Handled” error in Windows is a Blue Screen of Death (BSOD) error, which often happens due to faulty drivers, especially graphics card drivers. Below is a guide on how to fix this issue:

1.Boot into Safe Mode:

If your computer keeps restarting, you may need to boot into Safe Mode. You can do this by interrupting the normal boot process three consecutive times; use the reset or the power button on your computer to stop it during the boot, before it finishes loading Windows, and repeat this three times. After the third interruption, Windows should enter into the Automatic Repair environment. From there go to “Troubleshoot” -> “Advanced options” -> “Startup Settings” and then restart. Upon restart, press ‘4’ or ‘F4’ to start your PC in Safe Mode.

2.Update or Rollback Drivers:

   – Update Drivers: It’s possible that your current drivers are outdated or corrupt. Once in Safe Mode, you can try updating drivers by going into the Device Manager (right-click Start menu and select Device Manager), find the potentially problematic drivers marked with an exclamation point, right-click and select “Update driver”, and then choose “Search automatically for updated driver software”.

   – Roll Back Drivers: If you recently updated a driver before the BSOD started, rolling back to a previous version might solve the problem. In Device Manager, right-click on the driver in question, select “Properties”, go to the “Driver” tab and click on “Roll Back Driver” if available.

3.Rename Faulty File:

If you can identify a specific driver file from the error message (it will usually show up as “filename.sys”), you can rename this file from Command Prompt in Safe Mode. Access Command Prompt with admin privileges and type `ren C:\Windows\System32\drivers\[your_driver].sys [your_driver].old` to rename it, replacing `[your_driver]` with the name of your faulty file.

4.Use System Restore:

If you have previously created any restore points before these errors occurred, you may attempt to revert any recent changes using System Restore. Go to Control Panel -> Recovery -> Open System Restore -> Choose a different restore point -> Next -> Finish.

5.Check for Windows Updates:

Sometimes Microsoft releases updates that are designed to fix known bugs and issues with drivers and software compatibility. Always keep Windows updated by checking for any pending updates in Settings -> Update & Security -> Windows Update.

6.Perform SFC and DISM Scans:

Use Windows’ built-in tools – System File Checker (SFC) and Deployment Image Servicing and Management (DISM). Run Command Prompt as admin and input `sfc /scannow`. After SFC is done scanning, use DISM by typing `DISM /Online /Cleanup-Image /RestoreHealth`.

7.Check Hardware Issues:

Occasionally hardware problems can cause these BSODs. Make sure all internal components are seated correctly within your PC, including RAM sticks and GPU.

8.Reset Your PC or Clean Reinstall Windows:

As a last resort, if none of the above methods work, consider resetting your PC by going to Settings -> Update & Security -> Recovery -> Get started under Reset this PC or opting for a clean install of Windows using installation media.

Always backup important files regularly so that you can restore them if necessary after fixing errors such as these.