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 fixx21. Gathered from gameru.net forums. Originally created by Macron & hi_flyer.
Patch gathered from Gameinator forums
Read this article for more details:
Stalker Oblivion Lost Remake 2.5 Fixx21
NOT compatible with "S.T.A.L.K.E.R. OLR 2.5 English Patch v0.9.5" and below (critical crash), new english translation available (link below).
NEEDS "S.T.A.L.K.E.R. OLR 2.5 fixx19" or later (link below).
Fixx17 to 19 (Patch):
S.T.A.L.K.E.R. OLR 2.5 Patch fixx17 to 19
Optional (English translation):
S.T.A.L.K.E.R. OLR 2.5 English Patch v0.9.6 for fixx21