The difference between the disc version vs. the digital download version is probably the patch version. The digital download is probably on the latest patch.
Thus, perhaps in the original version of F.E.A.R. the game's architecture is not compatible with the new OS, and in a patch issued since the creation of the disc, the game was patched to be compatible with newer OS and other sorts of software.
I've found a compilation of F.E.A.R. patch notes. I haven't found a definitive answer. Here are possibilities:
- Fixed a crash that could occur when a client tried to rejoin or exit after a failed content download.
This assumes that you managed to get it working at all to achieve a failed content download, which may happen if the game tries to update itself. Although, this doesn't necessarily state that it's a consistent inability to play, but rather only after each "successful" failed content download.
This latest update corrects the loading issue with games saved before
the 1.05 patch and several other various fixes.
This may affect you if you're trying to continue older games saved.
This latest update fixes several issues.
Vague, so possibly making the gaming compatible with newer OSes, but one would figure that such a change would be worth mentioning.