The 32-bit EXE crashes when using >2GB RAM, common in Enemy Within.
Download Large Address Aware tool, select XComGame.exe, check "Large Address Aware", save. This allows up to 4GB.
Before fixing the problem, you must understand the anatomy of the file. file xcomenemyunknowncompletepackzip work
If you're looking to work with the "XCOMEnemyUnknownCompletePack.zip" file, here are some general steps: The 32-bit EXE crashes when using >2GB RAM,