windows 10 launch
The Windows 10 error message is being widely mocked. Above, a woman walks past a billboard for Windows 10, the latest operating system from Microsoft, during a launch event in Seoul on July 29, 2015. Jung Yeon-Je/AFP/Getty Images

Microsoft has updated its website with links to download the ISOs for Windows 10. With a product key handy, the ISOs can be used to run a clean install of the new operating system.

The ISO page also reveals the existence of two less-talked about versions: Windows 10 N and Windows 10 KN. What are they, and should you download them?

These versions are nothing new: they've been around since Windows XP. If you know your system has either Windows N or KN installed, it is important that you download the relevant version of Windows 10. Upgrade paths must follow the previous version, e.g. Windows 7 Pro N upgrades to Windows 10 Pro N.

The N version of Windows comes without a media player baked into the system. This version stems from a European Commission order back in 2004, which fined Microsoft €497 million for anti-competitive practices.

Bundling Windows Media Player, the commission decided, was unfair to competitors, so Microsoft should offer up an alternative version of Windows without the player. The company initially wanted to call this new version of Windows XP (the then-current version) "Reduced Media Edition," but the commission felt that the name would put off customers, so in the end, Europe was given "Windows N."

The KN version stems from an antitrust ruling in South Korea. This version removes Windows' media playing capabilities. At the time, it also removed the now-defunct Windows Messenger. The December 2005 ruling by the Korea Fair Trade Commission (KFTC) also fined Microsoft $34 million.

The Korean ruling also allowed for a second version, Windows K, which included the messaging and media player capabilities. Both versions also include links to competitor applications, unlike regular Windows. The difference between the European ruling and the South Korean ruling is that while Microsoft was allowed to continue selling regular Windows in the E.U., the company had to replace the version on store shelves in Korea with the new versions.

For both versions, Microsoft provides a "media feature pack" to restore the missing media playback functions. This pack has been updated for Windows 10 and can be downloaded from the Microsoft website.