What do you mean you can't locate the mp3's? In Windows check your LW Menu-Options & download location, in Mac, check your LW Prefs & Saving option. This will tell you where your mp3's are. If you're sharing your dwnld folder, then it will be listed on the top LH-side of your LW Library window. If still can't locate, then search within your desktop using your OS search engine be it Explorer/Search for the mp3's. Sorry I don't know how to add songs to the WMP. The mac version doesn't have that option!