.arch00 is F.E.A.R. Game Archive
Key Features: .ARCH00 File Extension
What is an .ARCH00 file?
Data archive format used by F.E.A.R. (First Encounter Assault Recon), a first-person shooter video game; includes game data referenced by the F.E.A.R. and required for the program to run; typically should not be opened manually, but can be modified using a third-party archive tool.