I am using Audacity 2.0.6 from the .exe installer which I just downloaded on a P.C. with Windows 7 Professional. The defaults were set to stereo and Line in like I used to have, but when I tried to record a You Tube track, I got only the top line recording. I am not very computer savvy, but I have enough nous to follow simple instructions, and would greatly appreciate any help to get Audacity working again.
I’m not a Windows elf, but we did write a thing about how to record internal audio.
So you are recording with a cable from audio out to the line in? Is it really a line-in, separate from the microphone input? If you are connecting to the only audio input you have, it may be a microphone input only, and it may be mono.
You will be better off to use Windows WASAPI to record YouTube: Tutorial - Recording Computer Playback on Windows.