Microsoft Windows 2000/XP Professional and Server were designed with multilanguage usage in mind. For example, the English language version is capable of handling input and display of numerous scripts including Arabic, Chinese, Japanese, Korean, Indic, Thai, Hebrew, and all the major European languages including Turkish. In addition, the user interface language can be changed independently of text input and display without installing a localized version of the product. The Multilanguage User Interface (MUI) provides this functionality; the current release offers twenty-three languages along with English. European, bi-directional, and Far East languages can be installed and selected as required at user level granularity. Such versatility is especially useful to companies having multilingual needs but who wish to simplify installation and maintenance as well as support multiple users speaking different languages on the same desktop or server. Additionally, the MUI is extremely useful to those that are involved in shipping products worldwide and are therefore involved in internationalization programming, localization, and language quality assurance. In this presentation, we look at MUI support from the user, programmer and network administrator viewpoints. We also examine MUI installation and directory structure, explain the difference between the system and user language, and show how an application can enumerate and query for available UI languages for both installation and run-time use. Demonstrations in contrasting user interface languages accompany the presentation.