Yeah I know Windows has had a UNIX compatibility layer for some time. I know that it is based on what was previousy a third party solution called Interix.
But I think it's expanding?? It seems bigger than the Windows Vista option and I don't recall Vista throwing in an SDK and calling it as such.
On the other hand, running Setup, it's offering me "Reinstall/Repair, or Uninstall". *shrug* Running install.