Along with Interplay's Shuttle, definitely one of the best space simulators ever released.Similar in concept to the better-known MS Flight Simulator, this game lets you pilot various spacecrafts, ranging from NASA space shuttles to futuristic space stations. Excellent details (especially planets in SVGA resolution), realistic space flight dynamics, and versatile camera & film options. The steep learning curve is eased by excellent on-line tutorials and help files.

Note: The game has long been discontinued by Microsoft, but its legacy lives on. Check out Orbiter, an outstanding (and free!) space flight simulation that is continually being developed and expanded.