Not anymore. After the lawsuit about including the web browser with the system they are no longer allowed to include undocumented features in their software. (citation needed)
no it wasn't then. It was around 2000 or so and more related to (as i remember) two things - securing government and enterprise contracts and public perception related to viruses and security. I was there as an employee in Visual Studio and distinctly remember the admonition from Brian Valentine that there were to be NO easter eggs in Win2K and on. They couldn't credibly say that they were in control of the security of the platform with people hiding doom levels in Excel and (in the case of Visual Studio) working slot machines...