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How to get rid of the uninstalled Antivirus product completely (for re-installation)?

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Many times the re-installation of an un-installed Antivirus becomes an issue, as the application installer reports the AV as still installed (refer below image for example).
Avira Screenshot
Our focus via this article is to resolve this issue.

But first, a bit of premise

Before we delve into the solution, we need to have a little background knowledge about Windows Management Instrumentation (or WMI).

WMI is best explained as a bridge which enables interaction between common scripting languages like VBScript and the Windows PowerShell scripting language and the O.S. management.

WMI defines the specifications due to which different system management utilities can share common O.S. level information like system settings etc. This information is typically stored in a common location called the WMI repository.

During the installation / un-installation of a system level application (like an Antivirus) the WMI database or repository is updated with the install status of the same. This is how Windows 7 knows you have a valid or alternate AV installed.

Sometimes it happens that the AV installer or uninstaller does not perform a clean job, and which then leads to an extra entry in the WMI repository. This extra entry is what causes false installation status during a re-install.

So what is the solution?

In order to resolve this issue, we are going to use the wbemtest tool. Kindly do take note of the below points before proceeding any further!

NOTE1: The tool which is being used to resolve the issue is quite powerful. It can lead to issues in your Windows Operating System if improperly used. You can get help from a knowledgeable friend to follow the mentioned steps.

Moreover, I suggest you go through the Technet article to have a better grasp of the wbemtest tool - http://technet.microsoft.com/en-us/library/cc785775(v=ws.10).aspx before starting.
NOTE2: Please note that we assume here that you have already removed the orphan entries from Windows Registry or have ensured that the discussed problem is not caused due to redundant entries in the registry. Refer the link http://www.experts-exchange.com/OS/Microsoft_Operating_Systems/Windows/XP/A_7411-Be-Registry-cleaner-of-yourself.html if you want to check the same. In case the registry is a non-issue, please proceed by executing the mentioned steps (in order!).

1.      Launch the command prompt (use WIN+R for RUN dialog – type cmd – press enter);

NOTE: You need an elevated prompt if you have logged in via a non-admin user in Windows 7. In this case, click on start menu, type cmd. When the result comes up as cmd.exe, right click and choose 'Run as Administrator'. This will launch the cmd console with Admin privileges.

2.      At In the command prompt, type in ‘wbemtest’ (without the quotes);

3.      The “Windows Management Instrument Tester” UI should open up as a result (refer Image 2 below)
 WMI Tester home
4.      Press the Connect button;

5.      You now need to enter the namespace. For Windows XP, use the namespace as "root\SecurityCenter" and for Windows 7, use "root\SecurityCenter2” (image 3 below)
 Connect UI
6.      Click on "Enum Instances" button and type in "AntivirusProduct" as the superclass name. a new window will open with the Query Result (image 4 below).
 Query Results
In case of a more than one AV installation, there will be more than one entry in the query result

7.      Double click on the entry (similar to what is shown in above image). This will open a pop-up with its associated attributes. Scroll down to ‘DisplayName’ attribute to check the "common" name. (Refer below image)
Key Attributes
8.       After you have verified the display attribute to confirm the GUID of the Antivirus which is not installed, you can select and remove the remnants of the not-installed Antivirus by selecting the GUID and clicking on the delete button.

9.      Exit from wbemtest application;

10.      Restart your system.

You can now try performing the initial steps again. Hope you are able to get the installation done this time!

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