Van Buren was the Codename given to Interplay's Fallout 3.
Text from "http://fallout.gamepedia.com/Van_Buren":
Featuring a fully 3D engine, that Black Isle had made for Baldur's Gate 3, commonly referred to as the Jefferson Engine. Black Isle Studios planned to include a dual combat system in the game that allowed for the player to choose real time (like Fallout 3 or Fallout Tactics) or turn-based combat (like Fallout 1 and 2). Due to Interplay's demands though, Josh Sawyer had stated that the emphasis would be on the turn-based version. Co-operative multiplayer was also going to be included in the game, again because of publisher requirements. In 2003, the game was canceled and the Black Isle employees were laid off. At that time the engine was about 95% done. You could create characters, use skills, perform both ranged and melee combat, save/load games and travel across maps. A tutorial level was done that would let the designers do all of the above. All areas but one had been designed. About 75% of the dialogue was done and at least 50% of the maps. BIS already had many of the character models and monster models.
The previous text is from "http://fallout.gamepedia.com/Van_Buren".
WARNING: This demo is extremely buggy.
You will need an archive program such as WinRar to open this .rar file and extract the contents.