Why %processor_architecture% always returns x86 instead of AMD64

You may be getting the wrong environment variable. If your application is a 32-bit application running on a 64-bit OS the process version of this environment variable will return x86. If you want to find the architecture of the machine, you can grab it from the following registry entry:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager\Environment\PROCESSOR_ARCHITECTURE

Or if you’re using .NET, then you can use this call to get it:

string arch = System.Environment.GetEnvironmentVariable("PROCESSOR_ARCHITECTURE", 
    EnvironmentVariableTarget.Machine);

From the command line you can try this:

reg query "HKLM\System\CurrentControlSet\Control\Session Manager\Environment" /v PROCESSOR_ARCHITECTURE

There is even a more simple solution using cmd:

ECHO %PROCESSOR_ARCHITECTURE%

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