Re-examining an old quote from Valve's Gabe Newell reveals a big gap in what we know about Doom's popularity. We all know Doom was so popular, so monumental, that it changed videogames forever. As a society, we're still obsessed with installing Doom on increasingly improbable devices, from pregnancy tests to vapes. But sometimes I run into an old factoid about Doom, some detail from its heyday that I'd forgotten, that still puts it in perspective. Like this one: back in 1995, Doom was installed on more PCs than Windows. I was reminded of this bit of trivia by re-reading an old PC Gamer magazine interview with John Carmack, published in November 2008, where the id Software programmer was reflecting on the benefits of open source and shareware. "We look back at the early days when the original Doom was shareware, and Microsoft did a study at the time that said there were more copies of Doom installed on computers than there were Windows 3.1. It's hard to characterise what exact value that is, to have people aware of your game but not paying you, but I certainly don't think it's been bad. Maybe we could have monetised it better than we would have thought of as a young company." More users than Windows sounds like it should be a gargantuan number, but you have to remember this anecdote predated the launch of Windows 95, in August 95, which is when the operating system truly took off. Personal computers weren't rare in the early '90s, but according to articles about the history of Windows, Microsoft sold only about 10 million copies of Windows 3.0 between 1990 and 1992, and an additional three million of Windows 3.1 within its first three months. In a 1996 interview, id Software president Jay Wilbur said that the shareware version of Doom had been downloaded 20 million times. That seems like an easy slam dunk comparison—Doom, which ran on DOS, was way bigger than Windows! In the early '90s, being installed on more computers than the most popular operating system of