Your Nero 6 program should come with a Nero Wave Editor. Open this program.
Go to START > CONTROL PANEL > SOUND SPEECH AUDIO DEVICES > ADJUST SYSTEM VOLUME > AUDIO and click the Volume for SOUND RECORDING. Using the checkbox select the recording source, in your case the microphone.
Go to Nero Wave Editor, click on Record button, choose recording format, click OK, then click record button to start recording. Once complete, click OK on record dialog box and then save the track onto hard disk.