I felt like being generous, fiddled around with mingw and managed to build a 64-bit windows binary of ghostlander's cpuminer that works on all cores as expected.

https://mega.co.nz/#!NQsjyArb!pwY2brGXdlyg8yuD3ko9Ly1nUuf6EFJev-7vc_pKZiQ

Donations welcome @ 9cbcfEfbjAKCbFa3kMjNi8qYruU628vPw3