Trying to set up my GT8 through my PC

[TJM2482]

Hey everyone, I recently borrowed my friend's Boss GT8. He told me he ran the stereo output(s) on the GT8 into his mic-in input on his laptop, and immediately heard himself through the speakers.

 

So I do the exact same thing, and I hear nothing. I tried on the mic-in AND the line-in, and nothing. I then thought it was my audio settings on Windows, but everything seems all set.

 

I can't imagine why it would work on my friend's Windows 7 laptop but not my Windows 7 desktop, which if anything has better hardware and probably a better stock onboard sound.

 

Can anyone help? I really want to get this working so I can try it out