Make Firefox user agent appear as Windows?

Is it possible to make Firefox or any other browser user agent appear like it would be Windows?

Because my online-banking refuses access due to my operating system. The only accepted OS is Windows.

Solution 1:

I'd imagine that they're just querying the user agent, which you can easily customize with an add-on like the User Agent Switcher.

Once you've installed that, Google can provide you with any number of Windows/Firefox user agent strings, and you can use the add-on to send the user agent of your choice when connecting to your banking site.

As an example, here's my user agent from Firefox on Windows 7.

Mozilla/5.0 (Windows NT 6.1; WOW64; rv:18.0) Gecko/20100101 Firefox/18.0