How do I enable the microphone?

Hi,

How do I enable the mic or any configuration to have this work? My is DEll Inspiron laptop 8500, and the Mic control is not in the volume control panel.  I used to plugged my guitar into the mic socket with my old IBM 1995 laptop,turned it volume up and played. It's been months and really frustrated. PLease help me.

P.s.  And where all the other options in volume properties have gone as I only have four options in my Dell?

Cheers,

Tiger.