Lee, Bongshin LeeBederson, Benjamin B.Microsoft Windows Explorer, the most widely used file browser in Microsoft Windows, shows almost all directories in the file system. However, most users usually access only a subset of the directories in their machine. If the file browser shows only the directories users are interested in, they can select the directory they want more easily and quickly. This paper introduces a configurable, scalable file system explorer that reduces selection time by showing only the directories users want to see. We give users an easy way to hide directories behind a special ellipsis node. In addition, those hidden directories are one click away. We present a preliminary field study conducted to validate the concept of Favorite Folders and a theoretical model to predict the performance times. Keywords: Windows Explorer, file browser, adaptive interfaces, customizable interfaces UMIACS-TR-2003-38 HCIL-TR-2003-12en-USTechnical Report