remove the .NET Framework Assistant for Firefox


  1. with regedit, go to HKEY_LOCAL_MACHINE\SOFTWARE\Mozilla\Firefox\Extensions
  2. Delete the {20a82645-c095-46ed-80e3-08825760534b} subkey
  3. go to %SYSTEMDRIVE%\Windows\Microsoft.NET\Framework\v3.5\Windows Presentation Foundation\DotNetAssistantExtension\ folder
  4. Delete the DotNetAssistantExtension folder and all its contents

source:

http://support.microsoft.com/kb/963707