Hi noticed quite a few problems with windows 7 sound, like myself, anyone who has SoundMax onboard audio might try downloading this updated driver, it worked for me.
It seems to be for Asus boards so don't know if it will work with others, you also get message of no codec installed and that it is not for this system, but has solved my sound issues.

This is the link SoundMax Integrated Digital Audio Driver v 5.12.01.4070 Rev. A - TechSpot Drivers

good luck.