It's not Windows all that runs in a computer, neither Linux. Apart from server editions, like AS/400, HP-UX and user oriented like OS/2 or MacOS, UNIX based or not, we also can find some unusual operating systems in an experimental state.

I'd like to name some of them that attracted my attention because of a special feature.

• Plan 9: it's a distributed OS, to run on several machines in a transparent way to the user.
• MenuetOS: a completly assembler programmed OS. It offers an assembler API to build applications.
• JNode: a java implemented OS, just a few assembler code to boot.
• ReactOS: a Windows compatible OS, written from scratch. Try to reuse drivers written for Windows.

None of them are finished at all, I mean, they are not everyday operating systems. And of course no modern devices are detected, just generic drivers are implemented. But they show that other ways different from Windows are possible.