It gives me an error message saying to use 'Setup64.exe', but I can't find it. I downloaded the AMD64 Far Cry upgrade software. I am using the Far Cry CD Set.
Well the AMD64 Upgrade is supposed to convert the 32-bit version to a 64-bit native version, or so at least I thought.

i think not. look it up to make sure.

There's a specific Far Cry version that is 64 bit. It must be purchased separately from the regular 32bit version.