Headset microphone not working

Ok so I had a USB logitech headset for about 2 years and it broke. I could hear sound and talk to people via skype and ventrilo just fine. Now the new headset I have bought plugs into the mic and speaker ports on the back of the comp, only problem is my computer is not recognizing the Mic.. I'm not really sure where to go from here, the headset is really awesome and comfortable but it looks like I am going to have to return it for a USB model. Does anyone know what might be wrong? I am noticing that in the device manager it is not locating my sound card.. Why would a usb headsets mic work opposed to an analog headset? I have a few conferences I need to part of coming up early next week and I need my mic working. Please help

Thanks, Mike

 

install your audio drivers (realtek) are most common if u have an onboard soundcard...