In changeset 88c3a1a3c2ff you'll find in test_api.py where I threw together a __path__ to compare against the one I was getting (which had 2 identical entries) on my Ubuntu 12.04 workstation.  The XP buildbot (http://buildbot.python.org/all/builders/x86%20XP-4%203.x) took issue with that (but non-windows was fine).

I was able to work around the difference (78d36d54391c), but I find the extra namespace portions surprising.  I'd like to get to the bottom of it.  I expect it has to do with how path entries are done on Windows, or perhaps with the way support.temp_cwd() iteracts with sys.path during testing.