How to hear my own voice through sound output

Is there software or a way to hear my own voice through the sound output? I am running a webcam feed, and very often when I am on skype with someone, the people watching the webcam feed can only hear the sound running from my pc, of course, and they can't hear me. I read around and some people said to just un-mute the line-in in the windows volume settings. However, it doesn't work for me. I managed to get it to work only once, but I have no idea how it happened, and I can't seem to repeat it.

I have a USB Logitech microphone, and an xfi pci sound card.

Any help is greatly appreciated.