How can I make my browser lie about my operating system?

I'm using Chromium (Version 30.0.1599.114 Ubuntu 12.10) under Linux. I'm trying to access a website that claims that it doesn't work under Linux. Of course, this is most likely crazy since the web is platform-independent (unless they're using some kind of evil plug-in).

I've used a user agent switcher to supply a Windows user agent, but to no avail. Upon viewing the source, it appears that the site is using Javascript to determine the operating system. I'm looking for a way to get my browser to report in Javascript that it is Windows or MacOS.

Do you know how to do it?

It seems that the javascript is using navigator.userAgent to infer your OS yet you have tried changing the useragent string.

It may be a bug _{(not that one, since you're running v30)}, you should go here to test if it is or not. If so you may have to try an alternative to the inbuilt dev tools that hopefully tries something fancy to get the same effect.