BSOD 0xc000021a - Cannot boot Win 10 at all

Hi Everyone.
Hopefully I can resolve this... I've tried everything to sort this out but nothing so far has yielded any positive results.

I cannot boot my Win 10 Pro at all. All efforts result in the error C00021a. We can go into what I've done if you like (no problem with that) but for the moment, can anyone tell me how to do an inplace upgrade (Win 10 to Win 10)? I think this will probably sort it out since DISM is unable to do anything constructive. Problem is that I cannot do an "upgrade" as to do that you must be running Windows (normal boot) from the start otherwise Windows Setup throws up an error telling me to start the machine normally and run the upgrade from the external media. Is there any way to do this upgrade to bypass this error? I can't boot normally so it's impossible to fulfill this criteria.

I have a pile of specialised music programs on this machine. I really don't want to have to install everything again as I have them set up "just so". Hope someone can help.

I read the initial admin post about installing a program to help you guys with dump files - but I can't install that either as the machine won't boot into Windows. Of course, I've run the usual sfc scans and dism routines. Sfc won't run and repair - will only check. HDD scans come up ok. Dism routines will check (all comes up ok) but not restore health. Therefore I'm really at the refresh stage. I have boot media to do this but can't get any further...

Can anyone help me with this? Here's hoping... thanks.

Hi, many thanks for replying.

I thought I'd gone down this route before (I've had this problem a while now). However, I decided to go through the procedure suggested anyway. Made sense.

Actually after copying over the regback files, and rebooting from the internal HDD the computer did spend much longer in the boot sequence. I really thought that the issue could be sorted. Then.... BSOD and C000021a error again.... Aaargh.

The first place I tried (when I first got the issue) was one of the malware forums as I thought that malware was the culprit.

However after many scans and log file outputs, the experts decided that I didn't have any malware problems, the machine was clean (should be as I do regular scans) and told me it would be best to try a Win10 forum where people more familiar to this sort of boot error could take a look.

What I *really* want to do at this stage is now perform an inplace upgrade from Win 10 to Win 10. I think that this is now my only option. However, I can't do that as in order to get the "upgrade" to run you have to boot into Windows first - which I can't!

Anyone know if this is possible by changing anything?

Alternatively, is there a way I can remove my installed Nvidia drivers from the command prompt to see if this is what is causing the issue?

I'm suspecting them as there were a couple of instances where I got WHEA errors a month or two before this C000021a error. Just rebooting solved it but I'm pretty sure if I can remove the video driver, (maybe replace it with a standard VGA driver" and then do an inplace upgrade, then I may be able to solve the entire problem. It's the last resort really as I think I'm now out of options here.

Unless you guys think otherwise !! Can anyone help further? :)

Ztruker said:

Is System restore enabled? If so you can boot to the Advanced Options menu from a Win 10 install or WinPE disc/flash drive then use System Restore to go back in time some.

System Restore Windows 10 - Windows 10 Forums

Advanced Startup Options - Boot to in Windows 10 - Windows 10 Forums

You could see if you can boot to Safe Mode then try to fix the problem, or select Low resolution mode.

Safe Mode - Start Windows 10 in - Windows 10 Forums

Hi. I appreciate that you're still with me on this...

I was 100% sure that system restore was enabled (there's no reason not to have it turned on). However, booting from a recovery USB shows that there are no restore points available.

No matter what I try, I cannot boot into safe mode. I get the same BSOD error.

chkdsk shows no errors.
I can scan using DISM but cannot repair anything due to Windows Resource Protection getting in the way.
sfc won't run either due to the same error.

DISM also throws up "Error 1" and won't proceed using various options.

It "must" be possible to run the upgrade again to fix this (I can't believe it isn't). I'm wondering now if it's possible to reinstall Windows 10 onto a new HDD and run the upgrade to the faulty disk partition. I'm determined to continue with this as others will undoubtedly come up against this. I don't do nasty things to my machine - I'm just a normal user with a genuine copy of Windows, good malware and (paid for) virus protection. The OS has failed due to something odd and I need to know what it is! I'm of course suspecting graphics driver or a windows update issue.

Anyone know how I can locate and uninstall my graphics drivers from the command line? Does that also need special access rights? Most stuff I read regarding changes and replacement of files states "use an elevated command prompt". How the hell can I do that in a recovery environment when I can't even log in???

I can't believe Microsoft has made it this difficult to repair a few system files! I've ordered a new HDD and will re-install to that so that at least I have a working system but I'm not giving up on this. Anyone have any other ideas?

It seems that you can use devcon.exe to disable drivers. It's a complex command line set but I'm going to see if I can disable all my NVidia drivers to see if that could be causing my issues. Hammer to crack a nut - but I'm running out of options... Will revert back when I have some results. I'm sure that I have corrupt system files but I'm gonna try this anyway.

Ztruker said:

Re: system restore. Microsoft sets it off by default. One of their stupider decisions regarding Windows 10.

There is no devcon.exe in Windows 10, at least not on any of my computers. Where did you read about it? Do you have a link?

Ah, never mind, found it: Windows Device Console (Devcon.exe) - Windows 10 hardware dev



I'm not sure how you can use it without being logged into the OS you want to manipulate.

Devcon actually works fine. I got it from the WDK. Had to install all of it onto another machine first to be able to extract devcon.exe (the 64 bit version I needed) but... after putting onto my errant hard drive it's a great utility! Can also work from a command prompt without having to log in first. Worth noting I think. I was able to disable my graphics easily once I'd identified what was loaded.

Doesn't help me though. Disabled graphics, nada, nothing... same error as before. Didn't make any difference at all.

I really am up the creek without a paddle here. I've no idea where to go now. There MUST be a solution to this BSOD somewhere. I've tried everything. At this rate I'm going to have to copy everything off as best I can and nuke the lot. I really didn't want to do that.

The main issue here is that I've completely lost faith in Windows 10 now. I didn't do anything untoward for this to happen. If my machine was full of viruses or I was using crap hardware then I could understand at least but this is a pretty standard setup, nothing nasty on there. Genuine Windows, good hardware and good protection - but it still failed. I'm thinking very seriously about going back to Windows 7. I never had a single squeak out of that (best operating system MS have ever made) and it was loaded onto 4 of my machines - two of which were thrashed every day. I only have Windows 10 on this (faulty) one and I can't repair it. I'm very concerned now...

Anyone have any other ideas??? I still need a way to perform an upgrade over an upgrade from the command line (as I can't boot the machine). I'm SURE that this will fix it if only I can find out how to do it. Anyone from Microsoft on here? You have a very disappointed customer!

I need a drink....