This is build 1935 of S.T.A.L.K.E.R. Shadow of Chernobyl, formally called S.T.A.L.K.E.R. Oblivion Lost. This was made by GSC Game World before they remade it and it was finally released in 2007. This was released by them after requests from fans of the game.
S.T.A.L.K.E.R. Oblivion Lost Remake 2.5 fixx19. Gathered from stalkerfrance archives website (gathered from russian site). Originally created by Macron & hi_flyer.
NOT compatible with "S.T.A.L.K.E.R. OLR 2.5 English Patch v0.9.4" (critical crash), new english translation available here: Stalker OLR 2.5 English translation v0.9.5
NEEDS "S.T.A.L.K.E.R. OLR 2.5 fixx17" (or later): Stalker OLR 2.5 + fixx17 part1, Stalker OLR 2.5 + fixx17 part 2