I'm running Windows 7 64 bit and have seen a lot about the Realtek HD audio not working well with 7. So far none of the fixes I've found have worked for me. I have deleted and reinstalled drivers and codecs from Asus and Realtek to no avail. HD audio pin is plugged into my mobo with no visible damage to either part. Options in BIOS are set to enable HD audio. I don't have speakers to test with, but headphones are recognized in both front and rear ports but no sound through those either. System displays drivers installed, up to date, and all functioning properly.
I just installed my new video card and I'm jonesing hard for some game time... really want to get this sound issue worked out!
For onboard sound/audio, you need to enable the Audio controller in the BIOS then you need to install WDM before installing the Audio drivers, and then only those drivers as per the motherboard specifications.