Are you using the mic slot or a differeng line-in? At any rate, try opening up a sound recording program. Even something as simple as that Windows sound recorder should help. Check to make sure the line-in isn't muted, and see if you can get a reaction out of the recording mechanism (try recording something, see if the equalizer bars jump, etc.). Also, sometimes I find that using a line-in slot just makes things really quiet, so you might have to up the volume.