In the future, please go to http://forum.blubrry.com for fast turnaround support and over 5 years of searchable questions ans answers on podcasting and PowerPress.
wp_bh_fan, i would not recommend PodPress, the original creator abandoned the plugin over 3 years ago. I know Tim is applying patches when sent to him, but as far as I know the plugin no longer has any long term plans to do anything innovative let alone keep up with latest iTunes standards.
goffkp21, PowerPress expects a URL, which will start with http://. If you enter a local folder path, PowerPress should display a warning that your URL is missing the http://.
More importantly, a valid media URL is what is needed in order for your media to be downloadable by other clients such as iTunes. When all said and done your feed will include a tag called "enclosure" and will look something like this: <enclosure url="http://example.com/path/to/media.mp3" size="180315003" type="audio/mp3" />.
I would recommend watching the PowerPress New User Basic Setup to get a solid understanding how to use the plugin as well as how to set it up: http://www.powerpresspodcast.com/2011/03/30/new-user-basic-setup/