Hi! I would really appreciate if someone help me on this, because I’m really an ignorant when it comes to computers 
I would like to record something with Audacity for example with my guitar directly plugged into the line in, so I play a backing track or metronome click or whatever for example with the media player, and the software records everything, not only the signal from the line in. Same goes with Sound Forge. Is it possible to record only the signal from the line in? I’m using headphones, so there’s no way for interference with the speakers or something. Thanks!
Hi!
You must have set the recording source to wave out/stereo mix (What-u-hear) on system recording control -panel?
On windows PC, select Start → Run… and type sndvol32 /r. Change the recording source to Line-In.
Juha
And it was so simple 
Thanks a lot!!!