Error code 0xc000021a - What is it?
Error code 0xc000021a occurs when the system is unable to start or there’s a failure in critical system processes. Normally, it would take about several seconds for the system to boot and while on the startup process, error code 0xc000021a may take place to block the system to boot up. Users will get a blue screen of death (BOSD) when this error occurs. When upgrading to Windows 10, be careful; you might encounter other error messages such as error code 8007002c.
Solution
Error Causes
There are several reasons why error code 0xc000021a occurs. It is important to have a full understanding of what caused the blue screen of death before attempting to fix the error by yourself. See below for a few common causes:
• Computer malware has infiltrated your device.
• Important files such as Winlogon.exe and Csrss.exe are damaged. Winlogon.exe file is responsible for handling the login and logout processes while Csrss.exe is a vital part of Microsoft Client or Server ‘Runtime Server Subsystem’. Once one of these files is damaged or deleted, a stop error will occur.
• When there are mismatched system files installed or system upgrading process failed or still incomplete.
• Premature unloading of Wbemprox.dll
• Newly installed third-party software is not compatible with the operating system.
• There are corrupted, outdated, or incorrectly configured device drivers.
• There’s insufficient space in the system partition. Once the system partition is full, certain errors such as error code 0xc000021a will manifest.
• Windows registry is corrupted or damaged due to a software or system change. This means there are registry entries that are not cleared after uninstalling an application.
Further Information and Manual Repair
In fixing error code 0xc000021a, you might want to try and manually do so. Manual repair methods can give users effective and efficient solutions, addressing the root problems in relation to Windows error codes. Once the manual repair method is correctly implemented, users will be able to resolve issues immediately. However, there might be instances when a Windows professional is needed. In such cases, seek help from a certified Windows expert or you might want to consider using an automated tool whenever necessary.
When the settings window opens, choose ACCOUNTS on it.
Windows will then go to the accounts settings page. Within that page, click on the Family & other users to open the setting for the chosen section on right. On the right settings, screen navigate to the lower section and click once with the left button on add someone else to this PC
When add someone else to this PC is clicked, pop up window will appear which will ask you to provide the persons email address and later on the password of his/her Microsoft account, after the required information is provided you are done, a new user has been added and he can use his Microsoft credentials on the login screen to use this computer.
This will open yet another pop-up giving you the option to create a Microsoft account for this person, to use a phone number instead of a Microsoft account, or to create a new email address for the user. Any of these options will create a new user for this computer with provided credentials but there is the last option at bottom of the pop-up which will allow you to create a local user only without a Microsoft account. This user will be able to use this computer, will not be able to transfer his document through various devices like he/she would if using a valid Microsoft account but it could use the computer and personalize it fully to his/her liking.
Once the link is clicked, you will be presented with a floating window requiring you to input needed information in order for the account to be created. You will need to provide username, password, and answers to 3 security questions.
Once all information has been provided, click on next and your new non-Microsoft local user has been created. Now when you click on Family & other users you will see that Windows has added a new user with the provided name to this computer. If you wish, you can add another user in the same manner, following the previous steps. Microsoft Windows does not have a limit for how many users can be on one computer so feel free to create as many as you like.
Click on Change account type.
Under account type, you will have the option to promote this user to an administrator if you wish or you can leave it as a standard user. 
Tracked as CVE-2021-34484, the “zero-day” flaw enables hackers to breach all versions of Windows (including Windows 10, Windows 11, and Windows Server 2022) and take control of your computer.
Microsoft mistakenly thought it had patched the vulnerability (which was first found in August) when it was publicly disclosed in October. But the fix itself was found to be flawed, something the company admitted, and this drew even more attention to the vulnerability. Microsoft subsequently promised to “take appropriate action to keep customers protected” but two weeks later, a new fix has still not arrived.
Luckily the third-party security specialist 0patch has beaten Microsoft to the punch with a ‘micropatch that it has now made available for all Windows users “Micropatches for this vulnerability will be free until Microsoft has issued an official fix," 0patch confirmed.
You will need to register for a 0patch account and install its download agent before the fix can be applied, but with 0patch fast becoming a go-to destination for hot fixes which beat software companies to the punch this is a no brainer. Hopes will be high that Microsoft can release an effective patch sooner rather than later but, until then, all Windows users must act now if they want to be safe.
Download 0patch here:
