How can record microphone sound with an audio recorder?

I suggest you use this recorder http://www.mp3-editor.net/mp3editing-software.html It is freeware and also an audio editor. You just click "New Record" on the left top and the recorder will pop up. In the "line-in" list, you should choose "mic" and then start recording. Easy right? If you still have problems, there are also many help contents within the program "Help" and on their website.