How to connect Dell XPS 15 (L502X) to my Surround Sound?

I'm trying to connect my Dell XPS 15 (L502X) to my Sony Surround Sound system (Sony BDVE3100). I've tried with an HDMI cable and through the SPDIF but I haven't had any luck.

I bought an SPDIF optical ( 1M TOSLINK Audio Optic Standard to 3.5mm Mini Plug Optical SPDIF Audio Cable OD2-in Consumer Electronics on Aliexpress.com) to connect it. The problem is that I'm only getting stereo through the surround sound. The computer doesn't seem to be recognizing that it's 5.1. I can't even find a way to configure 5.1 with this option.

When I plug in the HDMI directly to the sound system, the XPS doesn't recognize it at all. If I plug in the HDMI to my TV (which is connected to my surround sound through another HDMI) I can right click >> configure speakers but only Stereo comes up as an option, and when I test it, only stereo goes through the surround sound. I recently plugged my XPS into my fathers Bose surround sound with an HDMI and I could configure that to 5.1 output no problem. Could it be that there's a driver problem with the XPS (that's why it won't recognize it if I plug it in directly with an HDMI)?

So I'm at a loss on how to connect it. Any tips? I just installed the Realtek drives but that didn't seem to help me with my problem.

 

I'm thinking the problem might be that my XPS doesn't recognize the Sony BDVE3100 at all. I also can't connect to the system with bluetooth (my iPhone and room mates MAC have no problem doing this).