Cannot Boot Win10: Fix UEFI and bcdedit bootmgr

Fixing the "KMODE\_EXCEPTION\_NOT\_HANDLED" BSOD Error on a Windows 10 Pro System

If you're experiencing the "KMODE\_EXCEPTION\_NOT\_HANDLED" blue screen of death (BSOD) error on your Windows 10 Pro system, it can be caused by a variety of issues, including driver problems, hardware conflicts, or corrupted system files. In this article, we'll cover the steps to troubleshoot and fix this error, with a focus on editing the UEFI/BCD boot manager.

1. Check for Windows Updates

Before diving into more advanced troubleshooting steps, it's always a good idea to check for Windows updates. Microsoft frequently releases updates that address known issues and improve system stability. To check for updates, follow these steps:

1. Press the Windows key + I to open the Settings app.
2. Click on "Update & Security".
3. Click on "Check for updates".

Windows will automatically download and install any available updates. Once the updates are installed, restart your system and check if the BSOD error has been resolved.

2. Check for Driver Issues

Driver issues are a common cause of BSOD errors. To check for driver issues, follow these steps:

1. Press the Windows key + X and select "Device Manager" from the menu.
2. Expand the categories and look for any devices with a yellow exclamation mark.
3. Right-click on the device and select "Update driver".
4. Follow the prompts to update the driver.

If updating the driver doesn't resolve the issue, you can try uninstalling and reinstalling the driver. To do this, right-click on the device and select "Uninstall device", then restart your system. Windows will automatically reinstall the driver when you log back in.

3. Check for Hardware Conflicts

Hardware conflicts can also cause BSOD errors. To check for hardware conflicts, follow these steps:

1. Press the Windows key + R and type "devmgmt.msc" in the Run dialog box, then press Enter.
2. Click on the "View" menu and select "Show hidden devices".
3. Expand the "System Devices" category.
4. Look for any devices with a yellow exclamation mark.
5. Right-click on the device and select "Properties".
6. Click on the "Driver" tab and check if there are any conflicts.

If you find any conflicts, you can try updating the drivers for the conflicting devices or disabling the devices to see if the BSOD error is resolved.

4. Repair Corrupted System Files

Corrupted system files can also cause BSOD errors. To repair corrupted system files, follow these steps:

1. Press the Windows key + X and select "Command Prompt (Admin)" or "PowerShell (Admin)" from the menu.
2. Type the following command and press Enter:

This command will scan for and repair corrupted system files. Once the scan is complete, restart your system and check if the BSOD error has been resolved.

5. Edit the UEFI/BCD Boot Manager

If none of the above steps have resolved the BSOD error, you can try editing the UEFI/BCD boot manager. This is a more advanced troubleshooting step and should only be attempted if you're comfortable working with the command prompt.

1. Press the Windows key + X and select "Command Prompt (Admin)" or "PowerShell (Admin)" from the menu.
2. Type the following command and press Enter:

This command will back up the current boot configuration data (BCD) store to the C:\BCD\_Backup folder.

3. Type the following command and press Enter:

This command will set the boot menu policy to standard.

• BSOD errors can be caused by a variety of issues, including driver problems, hardware conflicts, or corrupted system files.
• To troubleshoot and fix the "KMODE\_EXCEPTION\_NOT\_HANDLED" BSOD error, check for Windows updates, check for driver issues, check for hardware conflicts, repair corrupted system files, and edit the UEFI/BCD boot manager (if necessary).
• References:
  • Driver Verifier
  • Driver Verifier Managed Code Guidelines
  • Driver Verifier Command-Line Options