The build tools do not run directly on windows right now.
You have a couple of options:
1) Use a linux virtual machine. Kivy provides a prebuilt VM image with python-for-android ready to use, as described at http://kivy.org/docs/guide/packaging-android.html#testdrive .
2) Use the cloud builder at http://android.kivy.org/ . There will hopefully be tools to access this more flexibly with buildozer in the nearish future.