1. Download and install Audacity
With most Windows and Linux audio devices, it is possible to record whatever sound the computer is currently playing, including internet radio streams.
In the drop-down menu on Audacity's Device Toolbar, choose “Wave Out” or “Stereo Mix” as the input source. (The exact name may be different, depending on your computer's sound drivers). On Windows, if you don't have a “Wave Out” or “Stereo Mix” option, or if it won't record, go to the system Control Panel and try to enable this option there. For instructions see: Using the Control Panel on the Wiki.
If this doesn't work on your computer, you can instead use a cable to connect your computer's “Line Out” (speaker) port to its “Line In” port, and use Audacity to record from Line In.
Note: Do not enable "software playthrough" when recording computer playback, because this creates a series of echoes.
Mac OS X
Record Your Voice / PC Sound Easily
Moo0 VoiceRecorder is a very simple sound recorder.
It is very easy to use, and you can start recording your "Only Voice" / "Voice and PC Sound" / "Only PC Sound" just by one click. It currently supports Wave and Mp3 encoding formats.
Also, since this program can capture any sounds on your PC, you may use it to record Internet radio, streaming music, Skype and even some sounds from your video files.
Directions above from Moo0 recorder
1. Download and install Cam Studio
2. Open ButtonBeats.com
3. Hit the record button
4. Highlight the area you want to record
5. Then It begins to record
6. Right click on the sys tray icon for cam studio and choose "stop" to stop recording