- you did a clean install of Windows 7
- You updated the sound drivers
for your Asus P5QD turbo
- you didn't install Cooledit again.
- you have an up to date BIOS
If this is all correct, I am basically stumped.
One long shot: can you disable the S/PDIF_OUT port? Once I had problems with the HDMI port from my video card, I had to disable that feature to get audio.
Have you checked your drivers for any error (small yellow triangle besides any of them)?