Well here goes my attempt at this.
Right click the speaker icon on the task bar and go to "Recording Devices". Set the mic as "Default Device" by right clicking on it and selecting the proper option.
Then double click the mic and goto the "Levels" tab and make sure its up all the way and not muted.
If that still don't work try going to the "Playback Devices" (right click speaker icon). Then going to "Levels" tab and make sure the mic is up and not muted.
If that still don't work then u might wanna do some Google searches about vista and microphones. U could also check for updates to your audio drivers.
I hope u get this fixed... cause I have had a **** of a time getting the front panel mic input working on my SB Xtremegamer card.