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    Technology Manager of Test Dept.


When you encounter startup error 0xc000021a in Windows 8 and 10, usually you’re reminded to restart the PC. But sometimes the error 0xc000021a still appears after the PC has been restarted. Some solutions about how to fix error 0xc000021a in Windows 8 and 10 will be provided.

Error 0xc000021a

Causes of Error 0xc000021a

Cause 1: Install malicious software or the software is incompatible with system. Besides, the computer may get viruses.

Cause 2: System files are missing or get damaged

Error 0xc000021a

Cause 3: BCD is a database of system configurations. If BCD is damaged or missing, it can’t be found when you try to boot Windows. Then error 0xc000021a happens.

Cause 4: Error 0xc000021a could be caused by hardware failure such as damaged graphics card, computer memory or disk. Especially when you have dual systems, Error 0xc000021a may also occur if there’s something wrong with the disk of one of the systems.

Cause of Error 0xc000021a

How to Fix Error 0xc000021a?

Solution One: Uninstall Malicious Software or Graphics Card

Step 1: Restart the PC. Hold down Power Button one or two times before manufacturer logo appears on the screen. Please select “Troubleshoot” after you enter Windows Recovery Environment.
select troubleshoot in windows safe mode
Step 2: Select “Startup Settings”. Then click “Restart”.
select startup settings in advanced options
clcik to restart PC in startup settings
Step 3: After restarting the PC, press “F4″ in “Startup Settings” screen. Then safe mode will be enabled.
press 4 to enable safe mode
Step 4: In safe mode, press “Win + R” key to go into “Windows settings” and select “Apps”. Click “Apps & features” then uninstall the software that was installed recently. Finally, restart your PC.
uninstall software in Windows 10

Solution Two: Use Startup Repair

Step 1: Connect your PC to Windows installation disk and start the PC.

Note: Please change the boot order in BIOS settings and put CD-ROM or Removable Devices as the first boot choice. Then your PC will boot from Windows installation disk.

change boot order in BIOS menu
Step 2: After booting from Windows installation disk, please click “Repair your computer” in the bottom-left corner when you enter the Windows installation screen.
Repair your computer
Step 3: Select “Troubleshoot”> “Advanced options”> “Startup Repair”. Then restart your PC after the recovery process completes.
startup repair in Windows
Tips: You can refer Solution One to enter Windows Recovery Environment. Then select “Troubleshoot”> “Advanced Options”> “Startup Repair”. Please be careful when you force Windows to start safe mode. It would be better if you use Windows installation disk to perform.

Solution Three: Use System File Check Tool to Scan and Fix Problems

Step 1: Repeat step 1 and 2 mentioned in Solution Two. Then select “Command Prompt” in “Advanced Options” screen.
command prompt
Step 2: Once command prompt pops up, type in: sfc /scannow. Press “Enter”.
Check and fix system files Windows 10
Tips: “sfc /scannow” command is to check whether system files get damaged and try to repair the damaged files.

Solution Four: Rebuild BCD

Step 1: Repeat step 1 and 2 mentioned in Solution Two. Then select “Command Prompt” in “Advanced Options” screen.
command prompt
Step 2: Once “Command prompt” pops up, type these commands in order: bootrec / fixmbr,  bootrec / fixboot,  bootrec / scanos,  bootrec / rebuildbcd.

Please press “Enter” after you type each command.

Repair or Rebuild BCD
Step 3: Executing above commands will scan Windows system and rebuild BCD.

Solution Five: Scan and Detect Bad Sectors of Hard Disk

Step 1: Download the hard disk detection tool HDD-SCAN. Then use it to scan the hard disk.
Step 2: Please wait until the scanning process finishes. If there are lots of bad sectors, they need to be repaired as soon as possible. Please refer to the solution to repair bad sectors.
windows 10 slow startup bad sector found in HDD Scan