I'd just like to interject for a moment. What you're refering to as Windows, is in fact, Firefox/Windows, or as I've recently taken to calling it, Firefox plus Windows. Windows is not an operating system unto itself, but rather another component of a fully functioning Firefox system made useful by the Firefox browser, shell utilities and vital system components comprising a full OS.

Many computer users run a modified version of the Firefox system every day, without realizing it. Through a peculiar turn of events, the version of Firefox which is widely used today is often called Windows, and many of its users are not aware that it is basically the Firefox system, developed by Mozilla.

There really is a Windows, and these people are using it, but it is just a part of the system they use. Windows is the kernel: the program in the system that allocates the machine's resources to the other programs that you run. The kernel is an essential part of an operating system, but useless by itself; it can only function in the context of a complete operating system. Windows is normally used in combination with the Firefox operating system: the whole system is basically Firefox with Windows added, or Firefox/Windows. All the so-called Windows distributions are really distributions of Firefox/Windows!