Kernel ntoskrnl.exe is missing or contains errors, Error 0xc0000221 in Windows 11

The 0xc0000221 error code is encountered by some Windows 11/10 users, right after the computer fails to boot. Several users report being stuck in an Automatic Repair loop with this error code. In this post, we will demystify the possible causes and then provide solutions to remedy the issue.

The full error message for this error code can be seen below-

Your PC Device needs to be repaired.

The operating system couldn’t be loaded because the kernel is missing or contains errors.

File:\WINDOWS\system32\ntoskrnl.exe

Error Code: 0xc0000221.

Possible causes

On investigating the issue and coming across different symptoms of this error, we narrowed it down to four culprits that might trigger the 0xc0000221 error code, as listed below:

1. Hardware issue created by new RAM or hard drive: There are a couple of reported cases where users started receiving this error after installing a second RAM stick or connecting a new slave HDD.
2. Secondary GPU: The issue is sometimes reported on computers that have an SLI or CrossFire setup. Whereby power supply is not capable of delivering enough power to sustain all connected devices.
3. System file corruption: The error code points towards a system-level problem that has to do with file corruption.
4. Third-party service is interrupting startup: There are reported cases where the error was triggered by a rogue third-party service.

Kernel ntoskrnl.exe is missing or contains errors, Error code 0xc0000221

We have provided some troubleshooting steps to help you remediate the 0xc0000221 error code. Below you have a collection of potential fixes that can aid you to successfully getting the issue resolved. We recommend you try the fixes in the order that they have been presented.

1. Boot into Safe Mode.
2. Perform an SFC, CHKDSK, and DISM scan, in that order.
3. Verify RAM for issues.
4. Remove secondary GPU and external HDDs/SSDs.
5. Perform System Restore.
6. Perform a Windows 10 OS repair install.

Let’s dig into the practical aspect of applying these solutions.

IMPORTANT: Whatever may be the reason, your priority should be to try and enter Safe Mode. If you can get into Safe Mode, great; else, you will have to use your Windows Installation Media.

1] Boot into Safe Mode

While in Safe Mode, your computer will start in a limited state with only the basic files and drivers needed for the Startup process. If your computer boots just fine into Safe Mode, then it’s likely the issue is been triggered by some software you previously installed.

Below is what you need to do, to troubleshoot this error once you have successfully booted into Safe Mode:

If you are unable to get past the startup screen, you can force the Advanced Startup Options screen by boot interrupting (Power on the PC, power off when the Windows logo appears. Repeat 2 or 3 times, always powering off when the Windows logo appears) the startup process.

If you are able to complete the booting process, you can also open the Settings Recovery tab by opening a Run dialog (Windows key + R)  and typing ms-settings:recovery, hit Enter. Then, simply click the Restart now button under Advanced startup.

Once you get to the Advanced Startup Options screen, select Troubleshoot and then click on Advanced options.

Inside Advanced options, click on Startup Settings, and then click the Restart button.

When you get to the Startup Settings again, press F4, F5 or F6 to boot with one of the three Safe Modes available.

If your computer boots successfully into Safe Mode, it’s safe to say the diagnosis, is a service from an application that you recently installed is triggering the error. In which case, you can start uninstalling recently installed programs that you feel could be causing the issue or, you can try to systematically exclude programs and services from the startup process until you manage to find the culprit.

But if you got the same 0xc0000221 error while booting in Safe Mode, proceed with the next fix below.

2] Perform an SFC, CHKDSK and DISM scan, in that order

By running these three built-in utilities designed to fix Windows file corruption, you can eliminate the possibility that the 0xc0000221 error code is not occurring due to a system file or file system corruption.

Below is how you can use these utilities to troubleshoot this error:

You begin by running the System File Checker. If you are unable to get past the startup screen, follow steps outlined above to get into the Advanced Startup Options menu, then go to Troubleshoot > Advanced Options > Command Prompt. Then, type the command below and hit Enter to run the System File Checker.

sfc /scannow

Once the sfc/scannow process is complete, restart your computer and see if the error persists. If it still is, return to an elevated Command prompt as shown above, and type in the following command and hit Enter, to run CHKDSK:

chkdsk /f C:

Note: In the above command, if your Windows installation is not residing on the C drive, change the letter accordingly.

When the procedure completes, reboot PC and see if you can get past the startup screen. If the same error repeats, return to the elevated Command Prompt as described above and copy and paste the following command and hit Enter, to run the DISM scan:

dism /online /cleanup-image /restorehealth

Once this process completes, restart your PC and see if it boots without the error. Still not resolved, you can try the next fix.

Fix: NTOSKRNL.exe BSOD on Windows

3] Verify RAM for issues

You can verify if your installed RAM modules are triggering this error. To do so, simply open up your PC and remove one of the modules (if you’re using two RAM sticks). If your PC boots successfully with only one RAM stick, try swapping the position of the two RAM sticks – issues sometimes occur when the faster memory is placed behind the slower memory.

Additionally, you can run a MemTest on both RAM sticks. If you confirm your RAM modules isn’t triggering this error, you can proceed with the next fix.

4] Remove secondary GPU and external HDDs/SSDs

Here, simply disconnect every unnecessary device – secondary HDD, external HDD, DVD optical drive, second GPU from SLI (or CrossFire setup), non-critical peripherals. Once you have stripped your PC to the barest minimum, power up your PC and see if it boots successfully. If it boots without the error code 0xc0000221, systematically re-connect the non-essential components until you manage to identify the culprit.

If this fix doesn’t remedy the issue, proceed with the next fix.

5] Perform System Restore

You might start experiencing this issue right after installing a Windows Update. In which case performing a System Restore could resolve the issue.

If you don’t have an appropriate System Restore point or the procedure failed, you can proceed with the next fix.

6] Perform a Windows OS repair install

If at this stage you’re still unable to resolve the 0xc0000221 error, you can repair install Windows – this will retain your personal files, settings and applications.

Let us know if something here helped you.

All the best!