The following is a guide on how to remove the Windows Presentation Foundation plugin in the Firefox web browser for good. If the plugin would not be blacklisted it would be possible to find out about its dll files by typing in about:plugins in the web browser address bar.

The dll NPWPF.dll is the the Windows Presentation Foundation plugin. Here are the steps to remove it from the Firefox web browser (and other Mozilla products) for good:

• Close the Firefox web browser and every other Mozilla software that is running.
• Go to x:\WINDOWS\Microsoft.NET\Framework\v3.5\Windows Presentation Foundation\ in windows Explorer where x is the drive letter where Windows is installed on the computer system.
• Locate the file NPWPF.dll
• Create a backup of the file by copying it to another location, e.g. to c:\backups\
• Delete the dll NPWPF.dll in the Windows Presentation Foundation folder
• Restart the computer

Open Firefox after the restart. The Windows Presentation Foundation plugin should not show up in the list of installed plugins anymore. There is a second step that might be necessary. There is also a Registry entry for the plugin. Do the following to remove the plugin from there as well:

• Open the Windows Registry, press [Windows key R], type regedit and hit [enter]
• Locate the Registry key HKEY_LOCAL_MACHINE\SOFTWARE\MozillaPlugins
• Locate the sub-key HKEY_LOCAL_MACHINE\SOFTWARE\MozillaPlugins\@microsoft.com/WPF,version=3.5
• Right-click the sub-key and select Export to backup the key before deleting it.
• Delete the key in the Registry
• Restart the computer system or kill and reload explorer.exe in Windows to load the Registry without the key.

This should get rid of the Windows Presentation Foundation plugin in Firefox for now.