For anyone stumbling across this now, this problem is a result of Windows not obeying the #!C:PathToVirtualenvScriptsPython.exe hashbang at the top of django-admin.py, and therefore running it with the wrong python.exe (evidently a virtualenv bug).
However, with virtualenv active, you can use the following command, which will result in the correct python being used, and everything being ok:
python C:PathToVirtualenvScriptsdjango-admin.py startproject <project_name>
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