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BSOD when running CCleaner

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Might have been coincidental. I use CCleaner on a daily basis - has never happened before. Also had another unrelated BSOD recently.
Was about to shut down the computer last night, only CCleaner was running - it happened half way through cleaning?

Bug check: 0xc000021a  


"The STOP 0xC000021A error occurs when either Winlogon.exe or Csrss.exe fails. When the Windows NT kernel detects that either of these processes has stopped, it stops the system and raises the STOP 0xC000021A error. This error may have several causes. Among them are the following:
  • Mismatched system files have been installed.
  • A Service Pack installation has failed.
  • A backup program that is used to restore a hard disk did not correctly restore files that may have been in use.
  • An incompatible third-party program has been installed."
I've not installed any new programs or drivers and I've also run a number of malware / rootkit scans in case - MalwareBytes, TDSSKiller, Hitman Pro and McAfee Stinger - no threats found.
Any ideas please?
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I have run chkdsk, is that what you mean? It was clean. I cannot run sfc scannow, as I have no installation disc for the operating system, but it is genuine....was installed by a PC World technician.


I have also set up Dr. Watson to trap user-mode program errors, as per instructions in the Microsoft article.

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I'd still like to see you do a sfc /scannow

You don't need the CD your OS was installed from, you just need any CD that matches your Windows version.

So using your friends, neighbours, workmates, are all valid alternatives.

And while you have it, make a copy as the day will come where you will need the install CD.

Your tower should have the CoA (Certificate of Authority) sticker on it with the Product Key proving your version is genuine.

The SFC command doesn't check for genuine software, and sometimes it can complete the scan without ever needing to reference the CD.

It depends on whether it finds files that have been corrupted and need re-copying from the CD.

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Thank you very much for helping me.


Security software - currently none, I am looking for a suitable one right now.


I have used CCleaner for years with no incidents so it is odd that it should suddenly become a problem.


Both BSOD's occurred towards the end of the cleaning process. Dr. Watson information didn't appear despite being set up to (has done before after a BSOD occurred).


I have uninstalled it now from my computer.....perhaps I need a fresh installation, that one was updated a number of times.


I've tried to run the SFC command several times - always prompted for the installation CD at start, so not been able to carry it through.


I've asked around, no-one has an installation disc. Arrrghh!


It is a genuine operating system though - validated by Microsoft.

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Security software - currently none, I am looking for a suitable one right now.

well, that's certainly brave of you, hopefully this hasn't been the norm and just a short-term situation.

2 good, free ones are AVG and Avast.  Others on this forum also recommend Microsoft Security Essentials and Comodo.


What is you OS?

Have you tried running CC from Safe Mode?

Does the PC have a 'make boot CD' icon either on the desktop in the Start Menu?

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Really appreciate your help and advice.


"What is your OS?" - My operating system is XP - yes, I know. :) But I can't change it at present. Installation CDs are expensive and I'm thinking I should really put that money towards a new computer / an upgrade, but I still need to have one for peace of mind sake and so I can run the SFC command.


"Have you tried running CC from Safe Mode?" No, I haven't reinstalled it yet.


"Does the PC have a 'make boot CD' icon either on the desktop in the Start Menu?" Not that I can see.

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if you have a good internet connection, you may be able to find an ISO image of XP that you could burn to CD.

it'll be almost 600meg though.

I would have thought the PC World Tech should have left you the CD he used, after all, you have paid for it.

he should have also placed the CoA sticker somewhere on your PC, which you'll need if you have to reload XP.


Safe Mode for XP is achieved by hitting F8 like a crazy person as soon as you turn the PC on.

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Thank you for that information.


Unbeknown to me when I knew little about computers, a computer technician put an unlicensed XP copy on my computer. The PC World technician who removed it said he couldn't give me the CD he had used because I hadn't had one to give to him. I only had the original Windows ME installation CD.


I don't even know what the Product Key is, the CoA (Certificate of Authority) sticker on it is Windows ME. Like I said before though the current XP operating system was validated by Microsoft and I was passed to get Microsoft Updates.


New computer is the answer, purse says otherwise. :wacko:

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Hello eloise - There is one more thing you might try to get sfc /scannow to work. See if there's a folder C:\i386 at the root of C:\ drive. If this folder does exist, it is usually a hidden folder so be sure to check the box "Show Hidden Files" first! If this folder does exist, restart your computer in safe mode, then run sfc /scannow as administrator (right click). When you are prompted for the installation CD, enter "C:\i386" as the path and cross your fingers. This may be hit or miss, since several of the sources where I found this tip claim that some but not all system files are copied here during installation.

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sounds to me like the PC Tech guy used a previously activated key - otherwise he would have peeled off the sticker from the installation CD and placed it on your PC - as he is bound to by Microsoft.

the Product Key is the 25 character string on the CoA that is unique to each Windows installation.


so, yes, yours is genuine (sort of) in that it has passed the activation process but you are buggered come re-installation time.

either you, the other PC's he is installing this onto or all of them, may eventually get the message "This version of Windows is not genuine.  You may be a victim of counterfeiting".

but with XP now out of it's support life cycle, maybe MS will no longer care.


but not to worry just yet, your BSoD is only happening with CC.

have you noticed on what CC was doing just before the BSoD occurred?


sometimes getting the first run of CC to complete in Safe Mode will then allow subsequent runs to complete in normal mode.

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Thank you very much for that useful information.


Derek891 - My concern when making any changes to my computer and reason number 10 (!) why I need an XP installation CD is that I can't use System Restore for some reason (used to be able to) - after I installed Service Pack 3 it stopped working. Whenever I have tried since then I get: "Restoration incomplete -- your computer cannot be restored to" no matter what checkpoint date I choose.


mta - Think you're spot on there. He didn't charge me for the XP installation CD, he just charged me for the work he carried out.


On both occasions CCleaner was coming towards the end of the cleaning process. It was like it knocked something out? On the second occasion I looked closely at the two processes mentioned below in Task Manager as it was running, to see if I could see either being ended - but I didn't see anything before the 2nd BSOD occurred (but then that occurs at the same time the error does I guess).


On both occasions it was STOP 0xC000021A error>>>>>




Note Follow the instructions in the Knowledge Base article to troubleshoot a process that shuts down with an exception. While you follow these instructions, monitor the following processes to troubleshoot the STOP 0xC000021A error:

  • Winlogon.exe
  • Csrss.exe

Note Most STOP 0xC000021A errors occur because Winlogon.exe fails.

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try the running of CC in Safe Mode and get back to us.


even though you don't have a Product Key for XP, it's probably still useful trying to get the CD as you will need it one day - maybe sooner than you think depending on this problem.  but no Key = no reloading XP.

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Ok will do later.


You have to have the Product Key in order to re-intall XP....mmm.


I previously heard that there is another way to get the Product Key via software?


Never done an operating system installation. Too advanced for me.

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during the installation of XP, it will ask for the Product Key, if you don't have one, you can tell it to skip it for now but it will ask for it later as Windows will then only work for 30 days until it will force you to activate it, it's then you will need the Key.


I tried that reverse engineering software about 2 years ago on my Office product, the Key it spat out wasn't even close to the one I had on my CD sleeve so I don't know how reliable that software is/was.

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Ok, I see, thank you for that information. Perhaps a search for a recommended one, got nothing to lose, if it's incorrect I'll be in the same position as I was before. At least I know now that it might be incorrect.


I reinstalled CCleaner and managed to run it in Safe Mode, so I proceeded to run it in Normal Mode - no problems. :)

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well, as far as your topic goes, a win at least.

good news.

you can continue running XP now until the next crisis !

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  • 1 month later...

You were all a great help to me here before and I am back hoping that you will answer these few questions for me, as we did discuss these particular issues (see above).


You may recall that I have a genuine ("sort of") copy of XP SP3 installed, but previously I didn't have an XP installation CD and I didn't know the Product Key.


mta - I managed to get the 25 digit Product Key - both Belarc and Magical Jelly Bean (!) Windows Key Finders gave me exactly the same code.


I have also managed to get a brand new genuine XP SP2 installation CD with COA + unused key - haven't seen any SP3 ones and Microsoft no longer distribute XP software. It says for distribution only with a new PC - is that ok?


Will a computer technician be able to reinstall XP SP3 using this and an update (although I'm not too bothered about the Service Pack, as it caused me problems before - I realise it's there for security reasons though). I'm wondering if the Service Pack is an optional choice when installing or if it's integrated and if it's integrated can it be updated to SP3?


Also, please confirm that this CD will enable me to carry out the sfc /scannow command (which was suggested here when I had the BSOD problem); when I previously tried to I was repeatedly asked for the XP installation CD.


This SP2 CD / SP3 computer difference is making me wonder.


A modern operating system would be better I know, but I am not able to get a new computer at present.

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there will be system file differences between SP2 and SP3 so doing a SFC /SCANNOW  you would need the XP version on the PC to match the version on the CD.

(it may work, and won't hurt if you do try but don't be surprised if it still says something along the lines of 'wrong CD, please insert correct XP CD')


as I may have said earlier, you can use any Product Key with any XP CD (it'll work on any SP).

so now you have an installation CD and hopefully your own valid Product Key you should be good to go.

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Thank you very much for your helpful response mta.  :)


So if a person had just Windows XP originally on their computer, once they had downloaded SP1, 2 or 3 that would leave them stuck when it came to the sfc /scannow command.......and in need of a new os installation CD. These additional Service Packs cause problems.......


I'll try, if no good I'll keep my eye out for an XP SP3 installation CD, even though it is now obsolete!


At least one of the problems I previously had should now be solved.

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Not to butt in, but I can add some relevant info, maybe. 

This won't help for a wrong product key number, but if that is good this may help. 

Other members are welcome to  chime in with a simpler method, this is just how I have reinstalled win xp before. 

You can probably do all this stuff yourself, save a trip to the computer shop. 


First, I am 99.9 percent sure that if you can get that win xp sp2 installation to boot and run then you can just install sp3 right into it. Then if it is a valid number, xp should go ahead and update for you, and you will have the folder called "C:\i386" mentioned by Derek891 up there in post #12.


Second, you should install sp3.  Its safer and just better, imho. 

Sp3 is a big file, about 316 mb.  I downloaded and saved it because I anticipate reinstalling win xp from time to time, and it is easier than downloading the sp3 installer every time. 


Third, once you get xp running like you want it, make and save a backup image. 

DennisD uses Macrium Reflect, the free version, and has had great success reinstalling with it. 


When I reset my win xp computer to factory original with the disks provided by the factory, it goes back to sp2. 

I then simply install sp3 which I have saved on an external USB HDD.

Just copy the file, named  WindowsXP-KB936929-SP3-x86-ENU.exe  to C:\ drive & click on it. After it installs you can delete the installer file from C:\ (but be sure it is saved somewhere). 

I have done this several times. 


More in a minute.  :)



General info about sp3:



Things to check before installing sp3:


Download page for sp3:




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Thank you very much ISO-later for that useful information, which I will keep, and for taking the time to help me.


This is what I bought, it was one of two, it looks genuine - edge to edge finely detailed holographic disc, the disc / COA is in pristine condition.




I purchased this in case there is ever a serious issue / for when reinstalling Windows is the only available option and also I was hoping to carry the sfc /scannow command. If this were a spare computer I would happily go ahead and attempt a fresh installation now, but I've never carried out one before, I wouldn't know where to start and I would be quite terrified that something would go wrong and I would be left with a black screen! I hate being without a computer. I'm quite keen to find out about installing Windows though, I should learn how to.


With regards the C:\i386 folder - I do have that, but if I remember rightly when I last attempted the sfc /scannow command some time ago it wasn't accepted and I still kept being prompted for the XP installation CD.

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