Fix: ERROR_THREAD_MODE_NOT_BACKGROUND 401 (0x191)

The ERROR_THREAD_MODE_NOT_BACKGROUND Windows system error, with code 401 (0x191), typically arises due to issues with a program or the OS. The error message reads, The thread is not in background processing mode.

Before you proceed to the solutions, reboot the PC, update the affected app, install the latest Windows updates, and disable any third-party antivirus software!

How can I fix ERROR_THREAD_MODE_NOT_BACKGROUND?

1. Check the affected program’s settings

Since the error is commonly program-centric, your primary approach should be to check the program’s dedicated settings and look for any inconsistencies or conflicts.

If you are unsure about the right setup, contact the app’s support team for more help!

2. Run the affected app in compatibility mode

1. Right-click on the affected program’s launcher (.exe file) and select Properties.
2. Go to the Compatibility tab, tick the checkbox for Run this program in compatibility mode for, and select an older iteration of Windows from the dropdown menu.
3. Click Apply and OK to save the changes, then reboot the PC and check for improvements.

3. Repair the corrupted system files

1. Press Windows + S to open Search, type Command Prompt in the text field, and click on Run as administrator.
2. Click Yes in the UAC prompt.
3. Paste the following DISM commands individually and hit Enter after each: DISM /Online /Cleanup-Image /CheckHealth DISM /Online /Cleanup-Image /ScanHealth DISM /Online /Cleanup-Image /RestoreHealth
4. Now, run this SFC scan command: sfc /scannow
5. Finally, reboot the PC to apply the changes.

Corrupted system files are just as likely to cause ERROR_THREAD_MODE_NOT_BACKGROUND 401 (0x191) in Windows. To fix this, run the DISM (Deployment Image Servicing and Management) and SFC (System File Checker) scans to replace all problematic files with their cached copies!

4. Reinstall the affected application

1. Press Windows + R to open Run, type appwiz.cpl in the text field, and hit Enter.
2. Select the program that is throwing the error from the list, and click on Uninstall.
3. Follow the on-screen instructions to complete the process, and then restart the PC.
4. Now, download and install the program from an official source.

When you are getting ERROR_THREAD_MODE_NOT_BACKGROUND The thread is not in background processing mode because the program wasn’t installed correctly the first time, reinstalling it will do the trick!

If a quick removal doesn’t work, use a top-rated software uninstaller to wipe all traces of the previous installation and then proceed to the reinstallation.

5. Perform a system restore

1. Press Windows + S to open Search, type Create a restore point, and click on the relevant result.
2. Click on the System Restore button.
3. Select the Choose a different restore point option, if available, and click Next.
4. Select the oldest restore point from the list and click Next.
5. Verify the details, click Finish, and then confirm the restore.

When nothing else works, and you can’t figure out the underlying cause, a system restore will allow you to revert all changes and take your PC back to a stable state. Just make sure to choose a restore point created before the issue first appeared!

One of the solutions here should have fixed the ERROR_THREAD_MODE_NOT_BACKGROUND system error in Windows. In case the problem persists, it’s best to contact the affected app’s developers for a fix.

Before you leave, discover the best Windows 11 performance settings and configure them to enjoy an error-free experience!

For any queries or to share which fix worked for you, drop a comment below.