Just bought some logitech z-5500's and had some questions:

my xtremegamer has a white jack that has a red glow and says optical, yet this isn't the type of hole for an optical cable. What is it for?

My motherboard has an optical out, but i get no sound when trying this.

I would like to know why the xtremegamer says optical and why im not getting sound from the optical out from my mobo