cant use headphones with computer, pretty sure its not the headphones.

Hello all, I'm having a problem with my turtle beach x12's, and just headphones in general in my computer. i got turtle beach headphones quite a while ago, and i haven't needed to use the mic until now. before i have tried using it, but it has never worked. i dismissed it as a problem with the headphones, but didn't care because i didn't really need to use the mic. no i would like to talk to my friends in-game, but my headphones still don't work. i tried plugging them into the ports on my case and motherboard but to no avail. then, i tried to use some old crappy Logitech headphones to see if it is a problem with my PC, and they didn't work either. the nature of the problem is as follows: i know its not a mic problem, because i can hear myself fine when i flip the little switch. when i plug my headphones in, it doesn't show up in the recording devices, even with show disabled/ unplugged checked. i don't really know how to troubleshoot beyond that so i would appreciate your help. thanks in advance, Theweasels1.

UPDATE: I installed skype to see if i could get it to work, and it said could not detect sound card. i have a really old mobo, so could it not have build in capabilities for recording? do i need a sound card?