Detect if running 32 bit program on 64 bit Windows OS

[Josh]

Is there a way to do that? I've tried 
getenv("PROCESSOR_ARCHITECTURE") and shell("echo 
%PROCESSOR_ARCHITECTURE%"), and both of them return "x86" instead 
of "AMD64" like cmd. I want to use this to run a 64 bit version 
of an external program if the OS is 64 bit, and the 32 bit 
version if not.