This paper details the design and evaluation of the Delphian Desktop, a mechanism for online spatial prediction of cursor movements in a Windows-lcons-Menus-Pointers (WIMP) environment. Interaction with WIMP-based interfaces often becomes a spatially challenging task when the physical interaction mediators are the common mouse and a high resolution, physically large display screen. These spatial challenges are especially evident in overly crowded Windows desktops. The Delphian Desktop integrates simple yet effective predictive spatial tracking and selection paradigms into ordinary WIMP environments in order to simplify and ease pointing tasks. Predictions are calculated by tracking cursor movements and estimating spatial intentions using a computationally inexpensive online algorithm based on estimating the movement direction and peak velocity. In testing the Delphian Desktop effectively shortened pointing time to faraway icons, and reduced the overall physical distance the mouse (and user hand) had to mechanically traverse. Copyright ACM.