No audio--Realtek and 7

Does your case have front panel audio jacks? If yes, are they connected properly and setup correctly in the BIOS? My ASUS motherboard has two different configurations for the front panel audio, HD Audio and Legacy AC97. Also the cable to the front panel audio jacks in my case has two connectors, HD audio and Legacy AC97. I don't know what happens if you get these crossed but it probably wouldn't hurt to double check them. You appear to done everything else trying to fix your problem.

I just built a system for a friend and had a very similar problem. It's got a
Gigabyte GA-H55M-S2V MB motherboard with Realtech audio device, 64 bit Win 7. I managed to get it working by doing this:

Go to control panel/realtech HD Audio Manager. In the top right corner where it says 'Device advanced Settings' click on that and change it to "Make front and rear output devices playback two different audio streams simultaneously"

This created a Speakers output device in Control Panel/Sound/Playback. Suddenly my sound started working (blasted me out of the room as all my volume controls were maxed ). This worked until the next reboot then the sound stopped again.

I went back in to Realtech HD Audio Manager and changed the setting back to the mute rear speaker option when headphones are plugged in. I clicked on the green icon of the Analog Back Panel connector and selected Front Speaker out.

That fixed my problem I'm not sure exactly why but it worked! Not sure if this will work for you but hopefully it might help.

Cheers

@Kano650

I have got the same motherboard with intel core i3 and a win 7... i'm having trouble connecting the front audio panel of the casing with the motherboard. I've read the manual and connected to a port named "F_audio" or something like that, but still there's no sound in the front panel. it's really annoying to connect my microphone/headphone everytime at the back of the casing. is there anything i need to change in the control panel? it's my new pc and it's been really a pain in the ass...
hoping you could help...

-F.A.Z