How to Fix: Can't Uninstall or Update Avast (Win10)

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Infopackets Reader Steve P. writes:

" Dear Dennis,

Recently my computer updated to Windows 10 October Update (2018). Since then, Avast antivirus reports that 'You are unprotected'. I have tried disabling and re-enabling Avast, but it doesn't help. I have also tried to uninstall Avast (in hopes of reinstalling it), but the uninstall hangs near the 99% mark and will not progress. When I abort the uninstall, it says 'You do not have sufficient access to uninstall Avast'. I have already verified that my user account has administrator access. I have tried updating avast but received an error 'Failed to update. The Avast service is not running'. I managed to get that running by starting the Avast service but now it says: 'The stub cannot run installer/updater executable'. I don't know what to do and need to stay protected with my antivirus. Can you please help? "

My response:

I asked Steve if he would like me to connect to his system using my remote desktop support service to have a closer look, and he agreed.

Below I will discuss my findings.

How to Fix: Can't Uninstall or Update Avast (Win10)

When I first connected to Steve's machine I tried to uninstall Avast manually through the Control Panel -> Programs and Features, but as Steve already mentioned, it would not progress past the 99% mark.

Avast offers an uninstall utility called 'avastclear.exe' which is a standalone installer used to uninstall Avast, which is typically used in cases where the uninstall fails to complete (as in Steve's case). Unfortunately the 'avastclear' did not work either, reporting an error that 'The stub cannot run installer/updater executable'.

I also tried downloading the full version of Avast but the installer would hang part way through and never progressed to completion. Oftentimes if you reinstall a program that isn't working properly, it resets permissions on files and clears the problem. Unfortunately that wasn't the case.

After a bit more digging, I discovered that Steve's Task Manager had over 25 'werfault.exe' tasks, which stands for "Windows Error Fault Reporting". Typically if a program crashes, the 'werfault.exe' Windows error reporting launches, then sends diagnostic information to Microsoft's servers (and also creates a log on the system). Usually the werfault executables disappear after the reporting is completed, but in Steve's case the tasks were still active.

After more research I reached the conclusion that Steve's operating system permissions were corrupted on the system, which was made worse by the Windows 10 October 2018 Update. I knew this to be true because virtually any program I tried to install would not complete, plus parts of his Start Menu were missing.

Unfortunately the only option from here was to backup the data on the system and reinstall Windows. This is a drastic measure, but in a cases like this, it was the only solution.

I understand most people reading this article may not need to do this, so I'll recap the steps I took (up to that point) in order to uninstall Avast.

How to Uninstall and Reinstall Avast (And Get it Working / Updated) - Step by Step

  1. First, bookmark this page as you will likely need to reboot the machine. To do so: press CTRL + D on the keyboard.
  2. Next, run chkdsk (check disk) on the C drive to ensure the file system isn't corrupt. A corrupt file system can corrupt a program install (or uninstall) and wreak havoc on everyday operations.

    To do so: click Start, then type in "cmd" (no quotes); wait for "CMD.EXE" or "Command Prompt" to appear in the list, then right click it and run as administrator. Highlight the text below:

    cd \
    echo this is a dummy line

    Right click over the above highlighted text, then right click the middle of the administrative command prompt window and select "Paste". The text you copied above should be output to the command line. If chkdsk is clean, it should say: "Windows has scanned the file system and found no problems."

    If you have a volume bitmap error (for example), you will need to correct it before proceeding.
  3. Next, try removing (or repairing) Avast through the Control Panel. Click Start -> Control Panel -> Programs and Features. Locate Avast and click Uninstall. If that doesn't work, right click Avast in the Programs and Features, and try the "repair" option.
  4. If it's still not working, download the avastclear.exe utility and launch it from an administrative command line. Running it from the administrative command line ensures that your user has administrative privileges in order to complete the operation.

    To do so: go back to the administrative command line you opened in Step #1 and then navigate to your download folder (or wherever you downloaded avastclear.exe), then launch avastclear.exe. The script below launches avastclear.exe from the download folder; to do so, highlight the text below using your mouse:

    cd \
    cd %userprofile%\downloads
    echo this is a dummy line

    Right click over the above highlighted text, then select "Copy". Next, right click the middle of the administrative command prompt window and select "Paste". The text you copied above should be output to the command line and the avastclear.exe program should run (and hopefully complete).
  5. If that doesn't work, you can also try rebooting into Safe Mode and running avastclear.exe. This can be tricky because Windows 10 no longer has the 'F8' option to boot into Safe Mode - you will need to set it using bcdedit or msconfig.
  6. If all else fails, have a professional look at the system - such as myself - described next.

You can download the full version of Avast (free) to reinstall here.

I hope that helps.

Additional 1-on-1 Support: From Dennis

If you can't uninstall Avast due to insufficient access or permissions, or if the avastclear.exe reports 'The stub cannot run installer/updater executable', it may be because the user account or the permissions on the operating system are corrupt. In that case, I can help using my remote desktop support service. Simply contact me, briefly describing the issue and I will get back to you as soon as possible.

Got a Computer Question or Problem? Ask Dennis!

I need more computer questions. If you have a computer question - or even a computer problem that needs fixing - please email me with your question so that I can write more articles like this one. I can't promise I'll respond to all the messages I receive (depending on the volume), but I'll do my best.

About the author: Dennis Faas is the owner and operator of With over 30 years of computing experience, Dennis' areas of expertise are a broad range and include PC hardware, Microsoft Windows, Linux, network administration, and virtualization. Dennis holds a Bachelors degree in Computer Science (1999) and has authored 6 books on the topics of MS Windows and PC Security. If you like the advice you received on this page, please up-vote / Like this page and share it with friends. For technical support inquiries, Dennis can be reached via Live chat online this site using the Zopim Chat service (currently located at the bottom left of the screen); optionally, you can contact Dennis through the website contact form.

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