Yep, sometimes its enabled, sometimes you have to do it yourself.
Follow these instructions
Click START
Click Control Panel
Open "Sound and Audio Devices"
Click the ADVANCED button in that little window
Wait for volume panel to open
Click on Options then select PROPERTIES
Scroll down in the big list until you reach an entry called "Mic".. It might be called something like "Mic Input" or "HD Mic"
Check the tick box next to that entry
Click OK
Now back on your volume control window there should be a new one at the end and it will be your mic, by default it's muted, so go ahead and un-tick that checkbox underneath it.
Adjust the volume as necessary and away you go.
dragon2309