On windows 2000, environment varables are recursively
expanded, so   
the comand os.path.expanduser('~\\test') will typically
yeld "%USERPROFILE%\\test".  This patch to ntpath.py
will recursively expand the '%' quoted varables until
either of the following happen:
a) It hits an environment varable it has already seen
b) The environment variable is not part of the environment.