Welcome RANDOLPH FREYTAG,
Thank you for reaching out to Microsoft Q&A forum.
I understand you are encountering the stop code 0xc000021a and want to know what DISM is.
Before proceeding, I’d like to clarify a couple of things:
- Are you able to boot into Windows, or are you stuck on a blue screen or recovery environment?
- Have you already tried any commands like SFC or startup repair?
In the meantime, you can try these steps:
What DISM is: you can find the AI answer previous to know clearly
About the code oxc000021a: you can try the steps below to troubleshoot the issue:
Option 1: Boot into Advanced Startup Repair
- Turn the device on and interrupt the boot process 2–3 times until recovery options appear
- Select Troubleshoot > Advanced options > Startup Repair
- Follow the on‑screen instructions
Option 2: Use System Restore (if available)
- Go to Troubleshoot > Advanced options > System Restore
- Choose a restore point before the issue started
- Complete the restoration process
I hope the steps above help you deal with your issue.
P.S: If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.