Check this link make sure this is your mother board.
http://download.asrock.com/manual/qig/CONROE945G-DVI.pdf
Front Panel Audio Header This is an interface for front
(9-pin HD_AUDIO1) panel audio cable that allows
(see p.2 No. 22) convenient connection and
control of audio devices.
From Page #18
1. High Definition Audio supports Jack Sensing, but the panel wire on the
chassis must support HDA to function correctly. Please follow the
instruction in our manual and chassis manual to install your system.
2. If you use AC’97 audio panel, please install it to the front panel audio
header as below:
A. Connect Mic_IN (MIC) to MIC2_L.
B. Connect Audio_R (RIN) to OUT2_R and Audio_L (LIN) to OUT2_L.
C. Connect Ground (GND) to Ground (GND).
D. MIC_RET and OUT_RET are for HD audio panel only. You don’t
need to connect them for AC’97 audio panel.
E. Enter BIOS Setup Utility. Enter Advanced Settings, and then select
Chipset Configuration. Set the Front Panel Control option from
[Auto] to [Enabled].
http://download.asrock.com/manual/qig/CONROE945G-DVI.pdf
Front Panel Audio Header This is an interface for front
(9-pin HD_AUDIO1) panel audio cable that allows
(see p.2 No. 22) convenient connection and
control of audio devices.

From Page #18
1. High Definition Audio supports Jack Sensing, but the panel wire on the
chassis must support HDA to function correctly. Please follow the
instruction in our manual and chassis manual to install your system.
2. If you use AC’97 audio panel, please install it to the front panel audio
header as below:
A. Connect Mic_IN (MIC) to MIC2_L.
B. Connect Audio_R (RIN) to OUT2_R and Audio_L (LIN) to OUT2_L.
C. Connect Ground (GND) to Ground (GND).
D. MIC_RET and OUT_RET are for HD audio panel only. You don’t
need to connect them for AC’97 audio panel.
E. Enter BIOS Setup Utility. Enter Advanced Settings, and then select
Chipset Configuration. Set the Front Panel Control option from
[Auto] to [Enabled].