Step1
First note that if your computer has a newer Intel based motherboard, the feature that allows you to do this may be disabled. Also I’ve heard this doesn’t work at all in Vista. The reason behind both of these is because the RIAA complained and convinced them that too many people were stealing music be re-recording internet radio. I think if you have a separate PCI sound card instead of just an onboard one, this will work for everyone with XP regardless of their motherboard though.
Step2
To set this up, you need to double click on the system volume icon in the lower right hand corner in the system tray. It's the little speaker shaped icon that you use to adjust the volume. Some common XP glitches can make that disappear so you can also get to it by clicking on sounds and Audio Devices on the control panel then clicking Advanced under device volume.
Step3
Recording Properties Either way, the extended volume control should open up. On the Options menu, click properties. Then change the selection to Recording and make sure that there is a checkbox next to "Stereo Mix." Usually there isn't a check there by default. Your menu should look very similar to the one in the attached screenshot. If you don't have an option for Stereo Mix, sorry, your system is one of the ones with that features disabled.
Step4
setting stereo mix Now that Stereo Mix is checked, press OK. This will replace the normal extended volume controls with the extended recording controls. Under each audio channel, there's a checkbox that says Select. What that does is sets the default recording device. By default, most computers will have the select button under Microphone because that's the most common channel people use to record audio. What you need to do is change the Stereo Mix channel to be the selected one. You also need to turn the volume way down. Just below the 2nd tick mark seems good on my system. You need to do this because that channel is outputting at a very high power but the system is expecting to receive recordings at a very low level. See the attached screenshot for an example of how it should look.
Step5
Assuming you don't have any other audio recording programs, you can open the Sound Recorder program that comes with Windows. You'll find it under Accessories > Entertainment. As soon as any sound is coming out of the speakers, press record and that's what will be recorded no matter what it is. Music, voices, game sound effects, anything!
Step6
Of course, sound recorder sucks so you'll probably want to get something better. I'd recommend Wavepad. It's a free program that offers way more functionality. You can graphically cut parts of sounds out and balance and EQ it and normalize and amplify it and all sorts of fun stuff. Plus you can save your files as MP3s. Wavepad has a tendency to reset the default recording channel as soon as the program open though but once you press record and it brings up the record options, you can choose which channel to record from then. Actually then you could skip every step except turning the volume down on the Stereo Mix channel.
Step7
So no matter what program you use, that's how you do it. If you play a digital rights management copy protected song, you can re-record it at full quality with no copy protection using this method. You can also record audio chats in IM programs but you have to mute your voice from within the IM program because as soon as you change from the mic to the stereo mixer, it will send that feed through the chat and basically bounce back everything they say which quickly creates a feedback loop. This re-recording can also work to quickly snag audio clips from DVDs while they're playing.