How to Fix Error 0xc000021a in Windows 8 & 10

The recent versions of Windows like Windows 8 and Windows 10 have done a lot to reverse the impression of Microsoft operating systems as being crash-prone, but even these newer and much more stable operating systems can still crash. One particularly annoying Windows error is error number 0xc000021A.

How to Fix Error 0xc000021a in Windows 8 & 10

This error message is one of the errors that means Windows itself has crashed, and your computer needs to restart. If you get this error, a big blue screen appears, telling you it’s collecting some error information and will then restart your computer for you. In small print under that, it gives the error code, 0xc000021A, and tells you that you can find out more information about the error online

Don’t panic! This error can be corrected so it won’t recur to bother you again. It’s most common for this error to occur after a Windows update.

Repair Windows Yourself

Since your Windows computer isn’t functioning normally, you’ll have to boot Windows manually.

  • To do that, hold down the “Shift” key on your keyboard while you select “Restart” from the power options for Windows. You may need to use a bootable Windows disc or bootable Windows USB drive if you can’t access the “Restart” function.
  1. A blue option screen should load that says, “Choose an option.” Select “Troubleshoot.”  Windows Troubleshoot
  2. In the Troubleshoot screen, select “Advanced Options.”                                                    advanced options
  3. Next, in Advanced Options, select “Startup Settings.”                                                          Start setting
  4. On the Startup Settings Screen,select “Disable driver signature enforcement” by pressing “F7” on your keyboard.Startup Settings
  5. Press “Enter” on your keyboard or the “Restart” button if one’s displayed.

Your computer will restart the way you’ve told it to. You can adjust your computer by using the different selections offered until you find the one that works for you.

Let Windows Repair Itself

Alternatively, you can choose the “Startup repair option,” where Windows automatically scans your computer to locate the problem.

  • Hold down the “Shift” key on your keyboard while you select “Restart” from the power options for Windows. You may need to use a bootable Windows disc or bootable Windows USB drive if you can’t access the “Restart” function.
  1. A blue option screen should load that says, “Choose an option.” Select “Troubleshoot.”  Windows Troubleshoot
  2. In the Troubleshoot screen, select “Advanced Options.”                                                    advanced options
  3. Next, select “Startup Repair,” which scans and tries repairing your computer automatically.  Startup Repair Win

Hopefully, Windows has found and repaired the problem that was causing your computer not to boot correctly.

Files That Cause Error “0xc000021A”

The two files that are responsible for the “0Xc000021A” error are “winlogon.exe” and “csrss.exe.” The first file is in charge of logging in and out of Windows, as the name suggests. The second file is a Windows server or client file. If either of these two files gets damaged or corrupted, the error can occur.

Windows can repair corrupted files and find missing files, but it can’t repair and fix hardware issues.

I hope this helped you resolve your Windows logon error without having to resort to resort to doing a clean install of Windows 8 or 10.

If you have found other ways to resolve this error, please let us know in the comments!

23 thoughts on “How to Fix Error 0xc000021a in Windows 8 & 10”

Nora says:
I am very happy my problem has been fixed and thank you very much
Allan L says:
Disable the driver got the computer to start…. but would have to do that every time after a restart… fixed the driver signature problem by following these instructions….

Be patient… it does take a little time…. but it fixed my problem.

Sharon Yeap says:
Worked for me!
Norton Customer Support says:
Same issue on my laptop! Auto repair does nothing. F7 does nothing but take me back to the same loop. WTH is going on here?
Ken Oats says:
I had this problem for weeks, looks like it is windows 10 trying to install its own driver. Eventually I remembered that earlier windows os that I always had trouble if I let windows update graphics driver that would end up with BSOD. After googling 0xc000021a problems it all pointed to graphics card problem.
My Solution was to go to device manager (if you can) and uninstall all display adapters and tick ” delete the driver soft ware for this device”. Go to manufactures site and download the latest drivers for you graphics card. In my case it was Nvidia GeForce.
Right click “This PC” in windows explorer, click on properties, then Advance System Settings, then the Hardware tab. Then choose “Device Installation Settings “. Now click ” No ( your device might not work as expected) then click on Save Changes. Now install your up to date drive you downloaded.
Hope this helps someone as it is annoying and very time consuming trying to find a resolution for this.
Steve says:
I had this exact problem. NOTHING in the instructions worked . . . . until out of sheer desperation I chose the option to start in another operating system (Windows 7) installed — which actually wasn’t installed (I had deleted it for preparation to use the disk as a backup of the main system disk). But the button showed Windows 7 so I tried that. Funnily enough, Windows 10 booted! WhThere must be a reason but now I know what to do the NEXT time this happens. And I’m sure it will.

Your mileage may vary. TGF Macs.

Jason says:
I got this error after a fresh format of the HDD & a fresh install of windows 10. So every site I have found online so far, have useless info because none fit the issue I am having. And everything that I could try is not working at all. Any help would be greatly appreciated thanks
Jay says:
I don’t mean to sound rude by saying this, but you’re being a little ignorant to the situation, Jason. Hopefully you’re no longer having issues with this error, but if you are or if someone who is sees this and is in the same boat I’ d like to help you out a little bit.

It’s pretty simple and for some people hard to deal with, but it could easily be a hardware issue. Technology isn’t like art, you can’t keep doing the same things and expect different results. If you’ve run the recommended troubleshooting steps (from what I’ve read this article does a good job explaining the issue and what to do) and you’re still running into issues, then I would suggest the same thing as the article and say that it is more than likely a hardware issue.

I’ve been reading up on the error and from what I’ve found it is not only related to winlogon and csrss. The issue can also be caused by a faulty CPU or RAM dims. I would also assume (based on personal experience with RAM and CPU issues) that it could be a faulty HDD with read/write errors.

I can assure you the information provided in this article is not useless and does fix the problem in certain situations. I hope this helps.

Tony Wood says:
Got the very same issues as most on here with windows 10 no matter what I try repair, safe mode, restore point etc all failed, Microsoft in all there wisdom advise solving from start menu that would be fine if I could get it to boot up Inthe first place thanks for your useless advice and rubbish
Tony W
Art says:
My friend you’re not alone. I had installed windows 10 for the 10th time and still get the same error 3 days after installation. It is useless
Tony Wood says:
Thanks for the reply I’m not very computer literate ended up getting my brother whose IT manager to have a look he tried various things and managed to get it up and running until I shutdown after restart got the same problem he tried the same thing but wouldn’t work eventually after managing to back-up the hard drive he then formatted the drive and re install windows 10 which seemed to have worked after a couple of days with no hitch I went on a weekend break going back on the computer trying to restart it it now tells me I have to register my windows 10 not sure if that means I have to purchase it now so haven’t really bothered with the computer since think I’ve just given up on it lol
Susan Ishak says:
Thank you Heather, you are a genius. My Toshiba Ultrabook just stopped working after a windows update and I googled the error code I was receiving which was ”0xc000021a” and found your blog. I did as you suggested and pressed F7 ”Disable driver signature enforcement” and my laptop is now working. What a relief and thanks again.
gmdsr says:
Received this error after windows recent windows 10 update. Tried all your suggestions and they all failed.
William says:
Got this after the latest win 10 update, started Forsa Horizon 3….crash. now nothing will work, it won’t even let me wipe my drives. Going to buy a new ssd and do a clean install if it doesn’t work after a fresh install.
Jn says:
I’Dell inspiron n5010. “Disable driver signature enforcement” solved my problem and I was able to boot my laptop successfully. However when I powered down and then switched the laptop back on again, I got the same error again. Surely there must be some tweak one can do in the registry for a lasting solution.
Steve says:
This has happened twice now to my Samsung ATIV Book 9 Spin, which has an SSD instead of HD. Both times, I was using Turbotax 2017, so I’m inclined to blame Turbotax. Turbotax 2016 worked fine last year. Every other program worked for 9 months or so, but right after I did my taxes in Jan/Feb, wham! (before I filed, of course). None of the repairs worked including the one that supposedly “keeps” your files but removes the Apps. I didn’t know to try the “Disable driver signature enforcement” on the first failure, so I just backed up everything I could to an external drive with the Samsung Recovery task (runs outside of Windows, and allows folder / file backup, but lacks specifics of size and date). The laptop worked fine for a couple months, until 2 days ago when I started pursuing working on my taxes again feverishly. And once again, wham! I haven’t been blue-screened in years, so something is definitely up. Turbotax is writing to an address / memory location it shouldn’t be would be my guess. Not that Microsoft isn’t culpable — there are lots of Windows 10 issues, some around visual presentation, and probably some around interfaces / inconsistent process calls. This time, I’ve tried everything offered on the Automatic Repair and Restart screens including the “Disable driver signature enforcement”, and nothing works. I may try to find a copy of Window 8 or even Windows 7 and go back to an unsupported version (since a search of the MS support pages confirms quickly that this is getting no confirmation or attention from Microsoft!!). Shame on both companies. I’m on the verge of switching to a Mac Book and Tax Pro.
AS says:
My son encountered the same problem when he force shutdown his HP laptop with Windows 10. I tried restarting the computer, start up repairs, system restore,resetting the pc,booting it on safe mode but it didn’t worked. Anyway, I checked on the error code”OXC000021a” and found your blog. I went again to start up settings and press ” F7 Disable driver signature enforcement” and the laptop worked after a couple of minutes. Thank you, thank you, thank son will be happy when he finds out that his laptop has been fixed.
Heather says:
You’re very Welcome AS. Glad to help out.
AS says:
Got the same problem on my son’s hp laptop when he force shut down the computer . I tried reestarting the computer,start up repairs, system restore, booting it on safe mode up to the point of it resetting it even going to youtube for fixing tutorials . Nothing happened. So I decided to check on the error code “OXC000021a” and found your blog. I went again to advanced options, chose “start up settings” and press F7″ Disable driver signature enforcement” “. After a few minutes, the computer restarted and it worked. Thank you, thank you,thank you… my son will be happy when he comes back from school and finds out that his computer is working.
Melanie Poche' says:
Mine also worked with the F7, however, as soon as you shut your computer down or restart it you will have to go through it again. I just want to warn you because give yourself time when you want to use your computer.
Bryan says:
For those that are getting this error, 9/10 times the Hard Disk somehow has gotten corrupted after an update. I have only had a couple successful repairs but it’s very few and far in between as I have delt with this issue numerous times here in my school district. To fix this issue you will need a clean installation of Windows and a new Hard Drive. Noticed that when I attempted to run Hard Drive surface tests in rescue environments, the hard drive tests couldn’t even detect the hard drive. Models this has happened to for me: Dell Latitude E5540, Dell Optiplex 3010, Dell Optiplex 3011 all-in-one, Lenovo thinkpad E535 and E545 models. All are either designed for Windows 7 or Windows 8 and all either had Western Digital or Toshiba Hard Disks. Thank you Microshaft for all your great products……Those trying to fix this issue with out doing a clean install, save yourself the headache, get a new Hard Disk or Solid State and install a clean version.
Brown County says:
Have had the same problem on multiple computers. Corrupt HDD after update seems to be the underlying problem. This fix here took care of problem every time. BTW if everything works after a clean install and a few days later the same problem occurs it could be that Windows has “updated” itself back into the original corrupted situation.
Tezza says:
I also am having the same problem with an ASUS f355m laptop from around the same date, have tried everything i have found on the net about this problem and STILL cant get it to boot. mine actually crashed during the update flashed an error screen for less than 3 seconds before it rebooted. so i didnt get a chance to read what it said.
Shweetha says:

I have been getting the same error code. I have a windows 8. I don’t have my disc either. My laptop asked to updated to windows 10, I tried to update it but it was not compatable. I have tried all of these options and non work. It’s a constant loop. I don’t know what to do anymore. Any advice that will be successful?

Rob Taylor says:
Just had this happen to me this morning. Initially got error L1C63X64.SYS and then stuck in the inescapable loop that other commenters describe above. Windows 10 won’t reset, can’t find any system restore points (there were loads) won’t safe boot, won’t self repair and won’t go back to the previous build.

The increasing recency of our posts suggests the latest Windows update has screwed something up enormously, or we’ve all fallen foul of the same super-smart malware.

Jack G says:
Same here. Blue Screen Of Death with 0xc000021a error after a Windows Update. None of the suggested fixes are working. Tried a home brew registry fix suggested on another site but some key instructions were left out and now I’m tapped out. Clean install is the next step I guess. Yay, Windows…
Bill says:
Same issue on my laptop! Auto repair does nothing. F7 does nothing but take me back to same loop. WTH is going on here?
Eric says:
I have 3 computer repair clients with the same exact issue. 2 of them are able boot into safe mode to use their PC but it will not boot normally. The hard drive in the third system completely died, so I replaced it with a brand new one and re-installed Windows 10. Now, only 1 week after that fresh installation with a brand new HDD, it shows this 0xc000021a error code and cannot even boot into safe mode. Hope someone can shed some helpful light on this frustrating issue!
RrnR says:
I have a Toshiba P50 laptop which has just started exhibiting this boot loop problem. It won’t boot from USB rescue media. I can boot to a DOS prompt window using the “Advanced” button, and that allowed me to inspect the C: drive, and run CHKDSK, which said it had repaired problems (and helpfully failed to save the log file), but it still won’t boot. The last time I shut it down it installed an update before turning off, so I suspect that update might be the culprit.
Edward says:
Same here as well. Neen trying to reinstall windows 10 pro back onto my samsumg laltop since monday night. It eomt get past the loading up for the first time. I contacted Microsoft and they said i jabe a corrupted harddrive. I followed the instructions to fix it with a dvd rom iso and again with a usb iso flash drive and still nothing. I always get the same blue screen with the same error code 0xc000021a what can be done or do i need to get a new harddrive? ?
JL says:
I have this problem. Unable to fix it with any of the tips found googling. Repairing fails. Unable to re-install windows.
Jason k says:
Windows 10 is just restarting in a continual loop-not allowing me to select a course of action to remedy this issue before restarting itself over and over, only to detect and notify you of the same issue. I’ve put the windows 10 disk in the drive before restarting however, it does not load the disk for me to select an alternative course of action, it just notifies you that your pic needs to restart over and over again. Further assistance would be appreciated.

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