I have a Centurion Windows Vista Business computer. I have unmuted the mic. I have a pink and green plug-ins on end of cord. There is a pink one on back of pc and on front but mic doesn't work. The only green connection on back of computer is very large, round and has metal pieces in it. Cannot plug the green one in anywhere. How do I get the mic to work? I go to school online and need to speak in my seminar classes. Thanks!