There is one report here, of the microphone jack not working. But the
thread conversation did not last long enough, to determine what the OP
tried to do to fix it.
http://vip.asus.com/forum/view.aspx?id=20080214093426781&board_id=1&m....
Also of interest, one poster had a problem using an add-in sound card
as well.
http://vip.asus.com/forum/view.aspx?id=20071222144710187&board_id=1&m....
In terms of your hardware, you have two places to connect a microphone.
There is a microphone jack on the back of the computer. There is
also a connection for microphone, on the AAFP audio header. I would
start by disconnecting the front audio, and testing the microphone
panel on the back of the computer. If jack detection is working,
when a plug is connected to the back of the computer, an audio wizard
may appear in response. If not, have a look through the Reaktek control
panels, and see if there is a reason why.
http://h10025.www1.hp.com/ewfrf/wc/fastFaqLiteDocument?lc=pt&cc=br&dl....
Since sound playback is working, that means you already have the Microsoft
HDAUDIO driver installed (something like KB888111). So this may just be
an issue with getting the Realtek panel set up to your liking.
Sometimes, a bad set of connections to the AAFP header, can
result in jack detection being broken. This is why, as a first
step, I recommend removing the front panel wiring. Since most
computer cases have AC'97 wiring, you should really only have
a total of five wires connected from the computer case, to the
header. Two for microphone, two for headphone, and a common
ground signal for them, for a total of five signals. No other
pins should have connections. Since the computer case
typically has seven wires, you'll have a leftover "ret_r" and
"ret_l" and those can be left dangling and disconnected.
Paul