i want to broadcast(livestream) the audio from pc 1 "line in" through pc 2 via network "LAN" because i have no available built in audio interface in pc 2..
you'll need to "broadcast" the audio from pc1 using winamp or any other audio streaming software, to local shoutcast/icecast server on the network. on pc2 you'll probably need to install Virtual Audio Cable in order to set up virtual soundcard as input. then use VLC or any other media player, to play the local stream to the VAC input.
The free program TeamViewer is able to stream audio from one PC to another via network, and in my experience the quality is quite decent as well (it auto-scales based on connection speed). Though it would have been nice to have more information so that I might provide alternate solutions, I believe you'll find TeamViewer to do exactly what you describe needing here.