You will have one copy in p2p & one in Library right? That's because it's the same file. It's not two copies.

Either that or else, the song was automatically imported into iTunes & you are sharing iTunes music files.

Control-click on the file & select the Delete option that shows. It will then give option of deleting from library or deleting from computer or sending to trash, something like that.

* Before you do that, control-click on the file, choose Get Information, then see where it's located on your computer for each copy of the music file. That will tell you if it's two copies in same location.