Join them together. You can use the Windows CLI copy command:
"copy <part1file> /b + <part2file> /b game.iso"
(use however many filenames it made (in order) followed by "/b" to indicate they are binary files.)
"copy <part1file> /b + <part2file> /b game.iso"
(use however many filenames it made (in order) followed by "/b" to indicate they are binary files.)