Why can't a 64-bit program run on a 32-bit copy of Windows? How does my PC know that I'm running a 64-bit program? Does the program have a piece of code telling Windows that it's a 64-bit program or does Windows simply fail to execute it?
I saw a significant difference in file size of the two versions of the same program, so I think it's the code that's different. Is it possible to modify the code and make the program run?