Download Firefox (
http://www.getfirefox.com )
Download "DownloadHelper" (
https://addons.mozilla.org/en-US/firefox/addon/3006 )
Go to Playlist.com, find your song, and download it through DownloadHelper. Save it as
{Song Artist} - {Song Title}.mp3 (You can name it whatever you'd like, I just like being clean. )
Voila.
That's what I do >_>