Basically the only tools you need are URL Helper, and Sothink Flash Decompiler. This will allow you to get songs right into mp3 format, and you won't have to use some sound recording software that makes it so you can't do anything else. Plus the bitrate is low, and so the songs are downloaded quickly, this is a perfect tool for Dial Up users.
I will not be held liable for anything. This is for educational purposes only.
Step 1: Find Your Song.
First go to napster and find the song you want to download. But do not click play yet.
Step 2: Open URL Helper
Open up URL Helper. If you don't have it then obtain it by any means you can but I will not be held liable if you obtain the program illegally. Once it is open, select the adapter your internet is running on and then start sniffing for URLs. Now click the play button for the song you want.
Step 3: Download the Song
Now a lot of links will pop up in URL helper. Look for the following link. http://18.104.22.168/stream.swf , Right click the link and then select Download Immediately. This will download it to what ever the save folder is and the default is c:\URLHelper\.
Step 4: Export the MP3
Okay now that the file has downloaded open up Sothink SWF Decompiler. If you do not have it obtain it but I will not be held liable if you obtain the program illegaly. Open up the .swf file, stop the music from playing. In the top left corner select stream.swf>Sound>streamsound 0. Finally click Export Resources, be sure Sound is set to Sound(*.wav,*.mp3) then choose where to export it to and click ok.
Now you have the song :)