Vista - Installing 32-bit app on 64-bit system failure message

I have attempted to install a particular 32-bit application of Vista Ultimate 64-bit. After running the setup.exe I receive the message that says:

"The version of this file is not compatible with the version of Windows you are running. Check your computer's system information to see whether you need an x86 ( 32-bit ) or x64 ( 64-bit ) version of the program, and then contact the software publisher."

The software installed successfully under Windows XP 32-bit. Other 32-bit software I installed under Vista Ultimate 64-bit was successful during the installation also. What about the software would cause Vista Ultimate 64-bit to stop the installation with the message above ?

Hello Eldiener,

What program are you tyring to install?

Some 32-bit programs will just not support running on 64-bit Vista even though most 32-bit programs can run fine. It just depends on what the program does.

Shawn

The program happens to be a help authoring tool, called ForeHelp, which I have continued to use to author help files under Windows XP 32-bit even though the company which produces it is no longer in business. Before you say "buy something else" I want to understand why Vista 64 would reject installing a 32-bit application when Windows XP does not. An answer that "Some 32-bit programs will just not support running on 64-bit Vista" really does not tell me anything why one 32-bit program is acceptable to be run under Vista 64 while another is not.

No problem Eldiener,

This can help give you a more detailed reason as to why some 32-bit programs will not run on a 64-bit OS.

32 bit and 64 bit explained | Gizmo's Freeware

All that link suggests is that the only reason a 32 bit application will not run in 64-bit Vista is that it has some 16 bit code. As a programmer I want to understand how Vista determines that the program has 16-bit code rather than 32-bit code. Is it in the format of an EXE or DLL that Vista-64 determines that ?

I couldn't tell you to be honest. You might see if Google may be able to get those kind of specific details. I hope you that you can find them.