"Partial" as the code uses sys.prefix in an attempt to locate 'w9xpopen.exe', but sys.prefix is not set if Python can't find it itself.  So this _still_ fails in Pythonwin, but I am committing the patch for 2 reasons:
* Embedded apps that set sys.prefix or use PYTHONHOME will work
* The exception raised on failure to find the executable is far more obvious