you install the sound card, that normally includes all the ins and outs of
the card. so if your speakers are working to play other stuff you should
have the microphone input. on the windows volume control it may not show
you the microphone volume control by default, but if you found the advanced
button for the booster that isn't a problem. my only other questions might
be if your card for some reason doesn't have a mic input and its really a
line-in jack instead, those are made for higher level inputs like from
external cd players. there is also the outside chance that either the card
or the jack is broke. is this a new computer, used, laptop, or what?? what
kind of sound card, on the mother board or separate card??