Windows 2000 is based on the Windows NT kernel and is sometimes referred to as Windows NT 5.0. Windows 2000 contains over 29 million lines of code, mainly written in C++ with over 8 million of those lines written for drivers.
Windows Vista is the successor to Windows XP in Microsoft's Windows line of operating systems. With the Vista iteration, Windows saw significant changes, both in aesthetic design and available features, with a focus on creating a more diverse and user-friendly experience.
Windows 7 is an operating system and the successor to Windows Vista. Windows 7 had Faster start-up time. Support for multi-touch on touch screen displays. A better overall performance compared to previous versions of Windows.
Windows 8 contains some of the biggest changes Microsoft has made to their operating system since Windows 95. It features new programming and technology that makes run faster than the previous versions. It also has a more streamlined look and feel. Windows 8 includes a tablet interface, called Metro.
Windows 8.1 has a start button on the desktop that opens the Start Screen. More customization to the Start screen including the ability to resize tiles, new backdrops, and the ability to use the desktop wallpaper as a backdrop to the Start Screen.
Windows 10 is the latest version of Microsoft Windows and an upgrade to Windows 8.1. Windows 10 shares a lot of the features first introduced with Windows 8 in addition to major features such as Cortana.