If I had a 32 bit version of Windows installed on a 64 bit capable machine, will the following command return "x86"?
On this specific situation(32 system over a 64 capable processor), it will return the value of the installed architecture of your Windows, so it will be x86.
I've just tested it on my machine(that is 64 capable):
Windows buttom + Break returned 32 bits installed system(my system is on portuguese):
And the echo %processor_architecture% command returned me x86: