I mentioned the Line-in because I connected a tape player to the Mic port on my laptop, which has no Line-in, and I believe it damaged the computer. When I played the tape player, the sound on the laptop was awful and I knew something was wrong. Immediately after that, the built-in wireless adapter stopped and never worked again.
I also connected the tape player to the Mic port on front of my desktop and, like the laptop, the sound was screechy. I then connected to a Line-in on back and that worked well.