How difficult can it be? (Line-in)

Hi

I have audio going through the Line-in but for some reason I cant hear it. The pc can detect audio but for some unknown reason only known to asus its not coming through my speakers, like the line-in is muted

ive looked all over windows and i think ive found the line-in volume controller, but its already unmuted.

all my settings in bios and my front audio connector are all set to HD audio, if that makes any difference i dont know.

can someone please enlighten me how to uncrack this asus mystery and let me in on the secret as to how to make line-in work.