Sound Issues: it won't record

My speakers play sound perfectly fine, but when I try to record an audio, it picks up nothing, even though I can hear it. Neither SoundBlaster nor Audacity record anything. To me, it seems like there's a missing link somewhere along the way, but since I know next to nothing about sound, I have no clue what it is, although I doubt it is external hardware. So far, I have not found any helpful info on the web...

If you have any ideas, please tell me,
Thanks!

Hi, do you have microphone ? Speaker can't record audio, for that, you have to use microphone.

Thanks for your response. I am not recording my voice but I'll try to explain my question better:
Let's say you want to record a couple words of a song in iTunes for a project. You open Microsoft's default Sound Recorder (or I often use Audacity), play the song, and press the "record" button as it is playing. The volume is on and you can hear the song, but the Sound Recorder does not record it.

Any idea why this is or how to fix it?
(PS this worked fine on my other computer)

Hm.. I also use Audacity for cutting some songs, but i don't use Record button. Just selection tool and Cut - Paste.

Check this link :
https://www.youtube.com/watch?v=RPhaKfWWF6Q

And you can read steps from here :
http://forum.audacityteam.org/viewtopic.php?f=36&t=4826
http://www.wikihow.com/Record-a-Song-With-Audacity

Thanks for your help, again. I changed a couple more settings and seeing the youtube video (and some others like it) I was able to toggle the correct setting. I needed to have "Stereo Mix" checked instead of "Line-in"

Thanks much~