Can't figure out how to play audio through line-in on laptop?

I have a dell inspiron 1525 which uses Sigmatel High Definition audio codec. Basically, I have an aux cord going into the headphone jack in my iPhone and I have the other end plugged into the microphone/Line-in jack on my laptop, I even went so far as to record myself saying a specific phrase needed to set up the microphone and played the audio from my phone through the aux cord into the mic input jack and it picked up the audio fine and set up and everything, but I can't figure out how to get it to take in the audio from the phone and stream it through my speakers on the laptop.

What's frustrating is, I can literally play music on my phone while plugged into the laptop while using my voice recorder on the laptop, and it will not only acknowledge the audio being streamed, it will record it perfectly and I can even play it back, but not stream it for some reason.

I tried going into audio settings and the mic is not muted. I also tried setting it up as a line in but when trying to access audio settings, I found that there's no option for me to unmute or adjust the volume settings for a line-in.

I also went in and altered my registry to regedit to try and manually insert a new binary value labeled "EnableInputMonitor" because apparently my laptop doesn't naturally have the ability to output audio directly from line-in, even though I can specify that it is a line-in when plugging in

I'm getting so frustrated with this.

Your computer will not recognize your iPhone as a microphone and just play music off of it. If you want that just download iTunes and play it through that, but other than that you can't. If it wasn't an iPhone than you'd be in a much better place as where you can share your files through the computer.