Let's say that you're a big government organization. Let's say that you have an application where your computers really, really need to be reliable. Like, say, NASA's computers on the International Space Station. What's the absolute last operating system you would choose for those computers?
Everyone I know in IT or programming would instantly say “Windows!”. Naturally, NASA chose Windows. Windows XP, to be precise.
But...even NASA eventually got tired of crashing, virus-vulnerable computers. They just switched to Linux (Debian 6).
Somewhere a Microsoft salesperson is being boiled in oil while Bill Gates stirs and Steve Ballmer piles on the coal...