And I forgot to mention that the resulting EXE (without old EXE) can be used for normal gaming.Hi everyone,
I created the EXE Unpacker for a DOS version of Civilization 1 (as suggested by you as the best version to play Civilization game). The code for the Unpacker and binary release are located at my GitHub page. All versions of civ.exe should work. The Unpacker restores the EXE to original compiled version IDA (and other disassemblers) can open and analyze. Note that DOS EXE overlays are present. The C compiler used to create EXE is Microsoft C 5.1 Optimizing Compiler.
I'm currently working on EXE overlays to be able to completely reconstitute original code.