The global .pdbrc file is determined by the %HOME% environment variable. However, this is not available out of the box on e.g. windows 7 systems. Here only %HOMEDRIVE% and %HOMEPATH% are defined.

Thus the usual approach to have a global .pdbrc file on windows is to define a %HOME% environment variable by hand. This could be avoided if the global .pdbrc would be determined by os.path.expanduser("~/.pdbrc"), which works on current windows and does the magic behind.

There are two possible approaches to improve this situation:
* explicitly mention in the docs that on windows a %HOME% varialbe need to be created manually
* patch pdb.py to use os.path.expanduser instead (see attached diff)

For reference, see also old discussion https://mail.python.org/pipermail/python-list/2005-October/349550.html.