Cannot Delete a Firefox Extension by Following the Instructions

My PC is an HP e9150t quad core machine using an Intel i7 CPU (920@2.67 GHz). I have 8 GB of RAM and am running Windows 7 Home Premium-64-Bit. I wanted to Remove the .NET Framework Assistant for Firefox, but the instructions that are given are incomplete for my computer.

Firefox provides instructions to delete the extensions, in general. However for the specific extension above, they refer to a Microsoft document which states:

"In the .NET Framework 3.5 SP1, the .NET Framework Assistant enables Firefox to use the ClickOnce technology that is included in the .NET Framework. The .NET Framework Assistant is added at the computer level so that its functionality can be used by all users at the computer level instead of at the user level. As a result, the Uninstall button is unavailable in the Firefox Add-ons menu because standard users are not permitted to uninstall machine-level components.

To resolve this issue, use one of the following methods:
Method 1: Download the Update to .NET Framework 3.5 SP1 for the .NET Framework Assistant 1.0 for Firefox
This update installs the .NET Framework Assistant on a per-user basis. As a result, the Uninstall button will be functional in the Firefox Add-ons menu.

Note This update is included in Windows 7 and in the .NET Framework 4.0.

To download the Update to .NET Framework 3.5 SP1 for the .NET Framework Assistant 1.0 for Firefox, visit the following Microsoft Web site:
http://www.microsoft.com/downloads/details.aspx?FamilyID=cecc62dc-96a7-4657-af91-6383ba034eab (http://www.microsoft.com/downloads/details.aspx?FamilyID=cecc62dc-96a7-4657-af91-6383ba034eab)
Method 2: Remove the .NET Framework Assistant for Firefox
To remove the .NET Framework Assistant for Firefox from your computer, follow these steps:
1.      Delete the registry key for the extension. To do this, use one of the following methods.
o      Use Registry Editor:
a.      Log on with an account that has Administrator permissions.
b.      Click Start, click Run, type regedit, and then press ENTER.
c.      Locate and then click the following registry subkey.

For x86-based computers:
HKEY_LOCAL_MACHINE\SOFTWARE\Mozilla\Firefox\Extensions
For x64-based computers:
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Mozilla\Firefox\Extensions
d.      Delete the {20a82645-c095-46ed-80e3-08825760534b} subkey.
o      Use a command prompt:
 .      Log on with an account that has Administrator permissions.
a.      Click Start, click Run, type cmd, and then press ENTER.
b.      At the command prompt, type the appropriate command, and then press ENTER.

For x86-based computers:
reg DELETE "HKLM\SOFTWARE\Mozilla\Firefox\Extensions" /v "{20a82645-c095-46ed-80e3-08825760534b}" /f
For x64-based computers:
reg DELETE "HKLM\SOFTWARE\Wow6432Node\Mozilla\Firefox\Extensions" /v "{20a82645-c095-46ed-80e3-08825760534b}" /f
2.      In the Firefox user agent, reset the changes that you made in step 1. To do this, follow these steps:
a.      Start Firefox, type about:config in the Firefox address bar.
b.      Scroll down or use Filter to find the following preference item:
general.useragent.extra.microsoftdotnet
c.      Right-click this item, and then click Reset.
d.      Restart Firefox
3.      Remove the .NET Framework extension files. To do this, follow these steps:
 .      Log on with an account that has Administrator permissions.
a.      Click Start, click Run, type explorer, and then press ENTER.
b.      Open the following folder:
%SYSTEMDRIVE%\Windows\Microsoft.NET\Framework\v3.5\Windows Presentation Foundation\DotNetAssistantExtension\
c.      Delete the DotNetAssistantExtension folder and all its contents"

After deleting the registry key, I closed down and then reopened Firefox. I proceeded with the following steps:

      Start Firefox, type about:config in the Firefox address bar.
b.      Scroll down or use Filter to find the following preference item:
general.useragent.extra.microsoftdotnet

However, there was no filter named "general.useragent.extra.microsoftdotnet" in my list. What you suggest I do now?

Thank you very much.
photoman11Asked:
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torimarCommented:
Just type "general.u" (without quotation marks!) inside the filter text box, this will help to avoid missing hits due to typos.

Is the preference item really not there?
There must be either a "general.useragent.extra.microsoftdotnet" or a "general.useragent.extra.firefox". By what you are told to do, the first entry would be reset to match the second one; so if you find the second one already, simply continue with the next uninstall steps.

If you see neither a "general.useragent.extra.microsoftdotnet" nor a "general.useragent.extra.firefox", create the latter one.
To do so, right click on any item in the list, select 'New > String', call the new item 'general.useragent.extra.microsoftdotnet' (without inverted commas), and set its value to "Firefox/3.6.3" (the '3.6.3' is the version number of your Firefox and may have to be adapted if your version is not the newest one; you will find it under 'Help > About Firefox' in the menu).
Then proceed with the uninstallation.


Alternatively, you could also simply proceed uninstalling the Dotnet assistant, then uninstall and reinstall Firefox: http://support.mozilla.com/en-US/kb/Uninstalling+Firefox
This method would be easier, but may require a backup of your bookmarks and user data: http://support.mozilla.com/en-US/kb/Backing+up+your+information
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torimarCommented:
Sorry, there is a severe error in my above comment:

"select 'New > String', call the new item 'general.useragent.extra.microsoftdotnet' (without inverted commas)"

must read:

"select 'New > String', call the new item 'general.useragent.extra.firefox' (without inverted commas)"
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