Google Operating System: Update Windows From Firefox And Opera:
"Many people that use Firefox or Opera, open Internet Explorer just to go to Windows Update to patch the security holes of their operating system (and, of course, create other security problems). In the last months, Windows Update site is very hard to use, it requires to have some Windows services like Automatic Updates and BITS set to automatic, it forces you to install a piece of spyware called Windows Genunine Advantage that will deactivate your OS if it thinks your copy isn't licensed (not yet, but Microsoft intends to do so).
But there's another way: WindizUpdate is a site that allows you to install Windows updates using Firefox and Opera. It installs a plug-in that detects what updates you need to install, downloads the setup for each update and installs them. It may not be official, but:
* updates are downloaded from Microsoft's site
* it doesn't collect personal identifiable information
* it doesn't require Windows Genunine Advantage and it doesn't install it
* you don't have to use Internet Explorer, neither the ActiveX for Windows Update
* you don't get dialogs that prompt you to restart the computer
If you still don't trust the site, you can find a forum where you can post questions or read other people's problems, without creating an account.
There are other ways to install the updates for Windows, but this is a great alternative to Microsoft's Windows Update."