Run an application only compatible with 32-bit on 64-bit machine

Here is a list of all wireless adapters compatible with Vista 64. These should also be compatible with Windows 7 since to my knowledge the network stack hasn't changed much.

If you run the application, in Task Manager it should have a *32 beside it to indicate it's 32-bit. I'm pretty sure they had this implemented in Server 2003, not positive though, hopefully someone can clarify.

You could also run it through PEiD. PEiD does not support 64-bit PEs, so it will choke if it's 64-bit.

There is also the famous GNU file for Windows. It will tell you all sorts of information about an executable.

Example:

$ file winrar-x64-392b1.exe
winrar-x64-392b1.exe: PE32+ executable for MS Windows (GUI)

$ file display.exe
display.exe: PE32 executable for MS Windows (GUI) Intel 80386 32-bit</pre>

As you can see, the 64-bit WinRAR installer is classified as PE32+, which signifies a 64-bit executable. The 32-bit application is simply PE32, a 32-bit executable.