to line-in jack.
Where did you get that from? Almost all Windows laptops are missing the Stereo Line-In jack and nobody owns a desktop any more. Does it actually say that (I know one machine which does).
what could have changed since yesterday?
I don’t remember if Win7 has Windows Enhanced Services, but that service is designed to automatically adjust your voice…and it hates music.
http://manual.audacityteam.org/o/man/faq_recording_troubleshooting.html#enhancements
So turn that off, and don’t leave Skype running in the background. Shut it down completely.
Given you don’t have a real Stereo Line-In connection, You could install a USB stereo adapter such as the Behringer UCA202.
That’s my stereo mixer instead of your turntable. Same problem.
Other people make devices which work.
Koz