This question maybe a bit historical, but we didn't have Superuser at the time. Around 2000 when I was starting my Computer science degree, a subject was Operating systems. The teacher asked us to list a few OS. I said Windows 95. I was immediately shot down. Windows 95 wasn't on OS, as it used DOS to boot up. The actual OS was DOS, Win 95 was just a graphical wrapper around it. I pointed that all trade magazines called Win95 an OS, but was told that they were run by laymen, and as a professional, I should know better. DOS was the only OS from Microsoft, at least till Win2K came out later that year. So 12 years on, I'm still not sure. Could Win 95 be considered an OS?