Unable to uninstall AVAST: "Stub cannot run installer/updater executable" (SOLVED)

On a client's computer, the following error occurred when the user tried to uninstall AVAST Free Antivirus: "The stub cannot run installer/updater executable 'C:\Program files\Avast Software\Avast\setup\Sfx\instup.ex' (code 0x3)". 

At first I tried to uninstall AVAST using Avast's removal utility (avastclear.exe) but the same error appeared again. Then I tried to download and install AVAST's latest version, but the same error message "the stub cannot run installer/updater executable…" still appeared at the installation's start.

After doing all these, I supposed that"The stub cannot run installer/updater executable 'C:\Program files\Avast Software\Avast\setup\Sfx\instup.ex' (code 0x3)" error occurred because AVAST installation was corrupted, so I decided to manually remove AVAST Free Antivirus. The procedure I followed is described below.

How to remove AVAST Antivirus manually.

Important: This tutorial contains detailed instructions on how to uninstall Avast antivirus manually in order to bypass the "Stub cannot run installer/updater executable" problem, during normal Avast uninstall process. Use the below procedure only if you cannot uninstall AVAST Antivirus either by using the normal procedure (program removal from Control Panel's "Programs and Features" / "Add/Remove Programs") or by using the AVAST uninstall utility (avastclear.exe).

Step 1. Scan your computer for viruses.

Some viruses or malicious programs can corrupt or modify your system files and settings. So, before you continue to troubleshoot the error "Code 0x3" problem during AVAST Install/Uninstall procedure , use this Malware Scan and Removal Guide to check and remove viruses or/and malicious programs that may be running on your computer.

Step 2: Download the “Geek Uninstaller” utility.

First, download the GEEK Uninstaller utility to remove all AVAST installation files and registry entries.

1. Open your browser at “http://www.geekuninstaller.com/download” webpage.

2. Click at the “Download Free” link.

3. “Save” the “geek.zip” file to your computer.

4. When the download is completed, navigate to your download folder and extract the “geek.zip” file.

Step 3: Use “Geek Uninstaller” utility to uninstall AVAST.

Force remove the AVAST Antivirus application using Geek uninstaller utility.

1. Navigate to the location where you extracted the “geek.zip” file in the previous step and double-click to run “geek” application.

2. At the “Geek Uninstaller” utility, right-click on AVAST Free Antivirus program and from the drop down menu, choose “Force Removal”.

3. Click on "Yes" to perform a force removal.

4. At the next screen review the registry entries to be removed and press “Finish” to remove them.

5. Close all “Geek Uninstaller” open windows.

6. Proceed to next step.

Step 4: Start your computer in Safe Mode.

Now start your Windows in Safe mode and prevent AVAST service and AVAST application from starting with Windows.

Windows 7, Vista & XP users:

1. Close all programs and reboot your computer.
2. Press the "F8" key as your computer is booting up, before the appearance of the Windows logo.
3. When the "Windows Advanced Options Menu" appears on your screen, use your keyboard arrow keys to highlight the “Safe Mode” option and then press "ENTER".

Windows 8 & 8.1 users*:

* Also works in Windows 7, Vista & XP.

1. Press “Windows”   + “R” keys to load the Run dialog box.

2. Type “msconfig” and press Enter.

3. Click the Boot tab and check the “Safe Boot” option”.

4. Click “OK” and restart your computer.

Note: In order to boot Windows in “Normal Mode” again, you have to uncheck the “Safe Boot” setting by using the same procedure.

Step 5. Disable AVAST Service.

In safe mode, navigate to Windows services and prevent the AVAST service from starting during Windows startup.

1. Simultaneously press the Windows key + R  keys to open the 'Run' command box.

2. In run command box, type: services.msc and press Enter.

3. Double click at AVAST Antivirus service and set the Startup type to Disabled.

4. Press OK to apply changes and close Services.

5. Proceed to Step 4. (DO NOT EXIT from Safe Mode)

Step 6. Remove AVAST Antivirus startup entry.

Finally, prevent AVAST Antivirus application from starting with Windows. To do that, you have to remove the Avast Antivirus (avastui) startup entry by using the System Configuration utility (msconfig).

1. Simultaneously press the Windows key + R  keys to open the 'Run' command box.

2. In run command box, type: msconfig and press Enter.

3. Select the Startup tab.

4. Uncheck the Avast Antivirus entry. ("C:\Program Files\AVAST Software\Avast\avastUI.exe" /nogui")

5. Press OK to apply changes and close the System Configuration utility.

6. Restart your computer when prompted.

You 're done!

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