If you want to get the media- songs, to WMP, all you do is
(1)open media player,
(2)click on the file tab and then click on
(3)add To Media Library---
(4) Click on By Searching Computer
Now you can choose your options of how you want the media player to search for the files, I usually choose new and existig files first, and then any files I download afterwards, I will choose the new files only (fast) option

NOTE: Make sure you click on the advanced tab so that you can uncheck the "Add Files Previously Deleted Fron The Media Library" option, or it will add files that you deleted.
Hope this helps.