The interface of World of Warcraft is built from XML files which describe its look and layout, and Lua files, which contain scripting functionality. This document is a short introduction into modifying these files to customize your interface. Customizing the interface is a very technical endeavor, and you should not attempt it unless you have a good working knowledge of XML and Lua. There is no official support for modifying the WoW interface. If you break it, you get to keep both pieces. :)

To start fresh, install the Interface Data and Art into your World of Warcraft folder; this creates a new directory called "Interface." This directory will override any built-in user interface you have already installed. To remove all customized UI, just remove the Interface directory. Be sure to never remove the Interface directory in the Data folder; only remove the top-level Interface directory that was created when first creating your custom interface. Whenever the game is updated, your customized files will not be modified, which means that you'll need to reinstall the Interface Data and Art and apply your changes to the new files.