Shoutbox

it's not always that easy,
basicly i see your options being either a cable or software,
a cable going from your speaker jack into your mic jack or,
you use some software, audacity claim to do it but i have no idea when i was doing music production i got a copy of cakewalk sonar which does it nicely and anytihng from here will probally do it
http://www.filedudes.com/files/Record_Speaker.html