First off - there is a newbies section for complex questions like these.
However - the mic input is amped up and is full of noise. Try using your line in input instead. You will find that you will, as mentioned, need a preamp of some sort. Also - if you are using a computer mic (like a labtec) you shouldnt expect anything good. I am guessing this is what you are attempting as most mic ins on soundcards are 1/8"