The Windows operating system is over 30 years old. In those 30 years, Windows has had it's share of innovations and setbacks. Sometimes it's been a big convoluted mess. This video shows someone who, using virtual machine software, upgrades a virtual PC starting with Dos 5 and going through the entire Windows family of OSes up to the current version Windows 7.

When I saw this video, it was pretty fascinating and the fact that a lot of the settings remained the same throughout the process was quite impressive. Obviously, Microsoft has taken the time to make sure that the upgrade process has some compatabilaty to it through the years.