I would use Audacity to record onto the computer. You can download Audacity for free here:
http://audacity.sourceforge.net/
and I would use Acoustica to mix/edit the recordings, you can download Acoustica for free here:
http://www.mp3machine.com/software/MixMultitrackStudio/
That is one of the best bets if you don't want to spend any money, if you want to spend money I advise you buy Adobe Audition or FL Studio (which is also known as
Fruity Loops) to do your recording and editing/mixing
Hope that helps.
Ciao, Joe