Feanor

Like everybody else one day I made a Windows Update and it installed something like 250M of .NET 3.5 "update". On top of it it also added an extension to Firefox, "Microsoft .NET Framework Assistant 1.0", without asking and with the "uninstall" option disabled. You can't uninstall the extension because it wasn't installed in the regular way. Here the description: http://msdn.microsoft.com/en-us/library/cc716877.aspx
Basically the extension is aimed to add Firefox the same "One Click" capability than IE when it comes to install/execute .NET applications from the Web. In case you want to get rid of this nice gift from Microsoft, here is the procedure: http://support.microsoft.com/kb/963707

Note that to remove the extension you need to edit the registry, edit Firefox about:config settings and then manually delete some directory/files from the disk.

This is bad. Actually MS knows that Firefox looks for the extensions in some locations. So via Windows Update Microsoft copies their stuff (linked to whatever else on the HD) so when you start Firefox it loads that stuff as "extension", despite you haven't actually installed as real extension neither you have the usual control over it as regular FF extension. I guess guys at Mozilla need to work around this.