As already explained in clan chat - If someone has the same problem, read this.
Line in requires no installation. However once plugged into the correct port (the pink slot or the one with the microphone icon next to it) you need to set your default microphone to line in.
WINDOWS XP:
Go into your sound settings (Taskbar, double click the sound icon)
Go to Options and hit Properties.
Select 'Recording' and you want Line-In selected.
It should work.
30-Jan-2010 15:58:30