well first you need to connect an output from your mixer into the line in port on your pc. if u avnt got a line in port then mic will do i suppose
Then u need a program like soundforge to record on as sound recorder only goes up to a minute i think. make sure to set the record input to lien in or mic depending where its plugged in to. You do this from the volumes menu you get from the bottom right taskbar on the desktop. hope that helps. any other probs just ask