There's a Tool called Audacity which is freeware available from Sourceforge
Among other things you can record sound from your PC, you can set it to use whatever input device you like.
You could even record yourself singing and use Audacity to mix it back onto a single track 
http://audacity.sourceforge.net/
http://renegademinds.com/TipsTricks/BasicRecordingforPodcasts/tabid/73/Default.aspx