This is apparently the build GSC showed off at GDC 2003.
Description (Translated by Google and cleanup up by me )
Download links:STALKER Oblivion Lost - build 1510/1511, Aug 19 2003.
Dead city: A legendary area of the old S.T.A.L.K.E.R. builds. This area was a prototype for Pripyat.
Generators: Another legendary area. Below the generators is a military base.
Military depot: An abandoned military base near an old swamp. Now the base of Freedom.
Dungeons: Abandoned tunnels under Chernobyl. Monolith control this area.
Two test levels: Test the A-Life system and physics.
present_demo.bat: Fly camera around the generator level.
present_demoA.bat: Same as above.
present_demoB.bat: Fly camera around sarcophagus.
present_demoC.bat: Fly camera around radar.
present_demoD.bat: Fly camera around military base.
present_level_ai_test_rats_flesh.bat: Test level with AI mice.
present_level_deadcity.bat: Dead city level.
present_level_generators.bat: Generator level.
present_level_military.bat: Military bases level.
present_level_physic.bat: Test level with ragdolls.
present_level_podval.bat: Sarcophagus level.
present_level_radar.bat: Radar level.
present_level_rats_flesh_anomaly.bat: Agroprom test level.
present_level_stalkers.bat: Agroprom S.T.A.L.K.E.R.s
present_level_vehicles.bat: Vehicle test level.
NOTE: I am still downloading this myself, so I'm not sure if it's real or not\virus infected. Chances are it's real. Theres a ton of youtube videos of this.