This tutorial teaches you what a Bigfile (.000) is, why you might see the error "Unable to open Bigfile Bigfile.000", and step-by-step methods to diagnose and fix it. Follow steps in order; try the quick checks first, then move to deeper fixes.
The Specific Fix:
The game tries to access Bigfile.000 for the base game, but fails if the DLC files (Bigfile01.dat, etc.) are present but corrupted. Ensure you have the latest patch installed. If you pirated the game, the "crack" often fails to redirect the file path correctly. In that scenario, the error is caused by the crack looking for the file in the wrong directory. Unable To Open Bigfile Bigfile.000
\x45\x46\x09\x0D → EnCase EWF7z\xBC\xAF\x27\x1C → 7-ZipCONE → VMware