Can't find anything online about it, basically whenever I try to apply any patches to Arx Fatalis, or manually delete the misc folder, this error shows up.

Occurs with the GOG version, Steam version, as well as the demo, and it completely stops me from being able to install Arx Liberatis, apply patches, or alter the misc folder short of uninstalling the game.

Will post pictures of exactly what I mean later, re-installing once again to see if that fixes anything.

GOG's version is already the latest official version, so you shouldn't need any patches in this case (I don't know about the Steam version).

Arx Libertatis copies game files to its own folder (you don't need to install it over top of the original game); if the normal installation method isn't working you can probably get it working by making a temporary copy of the installation folder somewhere (providing administrative elevation for the font if prompted) and then setting the Arx Libertatis installer to use that copied folder as the source for the game files.

Same problem here. Got the gog.com version, but I want to run my old German disc version in Arx Libertatis, but am unable to patch it, because Win7 locks the Arx.ttf file. Restart didn't help, Install as admin didn't help either. Even tried to remove the file handle in Sysinternals Process Explorer which is impossible as the System Process PID4 itself locks the file. Why on earth is that, Microsoft?

Contrary to any logic renaming arx.ttf to aarx.ttf fixed the issue for me. I could then apply the patch without problems...