Why can't i get my microphone to work on my computer?

I have a gigaware headset ( not sure about any other specs than the brand name ) it has 2 of the mm jacks. 1 for headset and 1 for the microphone. I know that the headset jack on it is broken so no sound is coming out through the headset but when I plug in the microphone side, no one that I try to talk to online can hear me, however I can hear myself incredibly loudly through my surround sound system. How do I separate the 2 devices so that I can hear people and computer sounds in general through my regular speakers, not hear myself at all when I use the microphone and insure that people I try to communicate with can hear me? I know it can be done because when I do this on my laptop it works just fine. Computer sounds from built in speakers, can't hear myself through the speakers, and other people can hear me just fine. Please leave a detailed answer because I am not that computer sav vy lol :)