There are many operating system out there, but the newest Windows operating systems out there are Windows XP, Windows Vista, and Windows 7. While new computers are usually sold with the newest operating system, there are people out there who bought a computer a few years ago and they still use an older operating system. Generally speaking, if a person has a Windows XP or newer operating system, then there is not such a big reason to upgrade. Newer operating systems may have more features, but they also may require more system resources such as RAM. Older computers may not have enough RAM to use effectively the newest operating system.