Free program to play guitar on my computer?

Hey, does anyone know of a free program that you can plug my guitar directly to my computer and playing live? Yes, I recognize the sound will be terrible without a pre-amplifier. We really have a fancy schmancy program, but is not available for me right now, so I'm just looking for a way to play without disturbing my roommate (the old amplifier with headphones is not always practical in my situation). Anyone?

http://audacity.sourceforge.net/download/

Twins Electronic Jam (guitar computer)