[ddouglass]

First thing is Hoster does not record so the microphone on your laptop will not work with it. Hoster only broadcasts the sound from the karaoke songs you play to your speakers or to the Line Out to be processed and amplified by outside equipment. It does not activate or use the Line In/Microphone Input.
As far as your Vista I don't have it, but I would think it should be in the same place as with XP. If you have the sound control (small speaker) on the taskbar then double click on it and check the Line In setting and uncheck the mute box. If the speaker is not on the task bar then go to the control panel/ Sounds and Audio Devices and check the box to add it to the task bar.