iw3mp.exe error, no stereo mix

[YJMfan]

I got this error playing COD4 after a new MB and fresh install on new HD. I looked around the net and and all I find relates to enabling stereo mix under sound/recording options. My problem is there is no stereo mix icon for me to enable. Even when I click show hidden it is not there. Can this be downloaded? Here is a link a friend gave me that describes the problem http://en.kioskea.net/faq/4482-cod-4-crashes-iw3mp-exe-has-stopped-working



System:
AMD 965 BE 3.4 Ghz
Asus Crosshair Formula IV
G.Skill Ram 8G
XFX 5770 Crossfire
Ultra X4 850w PSU
Corsair H50
HAF 922
Win 7 HP

My System Specs

 

[SleeStak]

If you are using the SupremeFX X-FI for audio make sure you have the latest audio driver installed available from Asus for the Crosshair IV Formula not the Windows 7 audio driver that is installed by default sometimes on a fresh Windows 7 install and see if that makes any difference