Well, can't help with the registry, but I suppose you could search google for "edit system variables path registry" and find the hard way. The easy way is:
You need to add the path of the directory where you keep myscript.py to your system path. You do this by going to Control Panel | System | Advanced | Environmental Variables. At the bottom under System Variables, edit the variable PATH and add the directory where you want to keep your Python scripts. rpd -- http://mail.python.org/mailman/listinfo/python-list