Some older PC cases don’t support auto-detection of mic’s or speakers connected to the front ports. In these cases your front connected microphone or headphones may not work until you “Disable front panel jack detection”.
Goto “Realtek HD Audio Manager” – “Connector Settings” – “Disable front panel jack detection”.
related link – http://mybroadband.co.za/vb/archive/index.php/t-82992.html
Mimesis1 