It sounds like you are wanting to record the same audio that is played back through the speakers.
In Windows XP, this may work a little different.
Under the sound properties in control panel, you should see the recording and sound section with a volume button just below each. Click this Volume button.
Next, click Options and select properties.
Here, you should be able to put a check next to the options you want as recording devices. Put a check next to Stereo Mix.
This should now be added to the volume category. Check the box below it to enable it as a selectable device for Stereo Mix.
I hope this answers your question. :)
In Windows XP, this may work a little different.
Under the sound properties in control panel, you should see the recording and sound section with a volume button just below each. Click this Volume button.
Next, click Options and select properties.
Here, you should be able to put a check next to the options you want as recording devices. Put a check next to Stereo Mix.
This should now be added to the volume category. Check the box below it to enable it as a selectable device for Stereo Mix.
I hope this answers your question. :)