DC7700 can't detect and install sound card after update to Windows 7

Question

I've been trying to get the sound on my HP DC7700 Ultra Slim desktops to work for a few months now (I'm a teacher at a high school, so I have about 100+ of them to take care of). I've upgraded them from XP to Windows 7, and the computers no longer recognize the sound card.
I have tried installing the Realtek driver from their site and HP's, I've tried updating the UAA architecture as suggested in other posts here and here.
In device manager, all hardware has been detected and correct drivers have been installed, including PCI and chipset drivers. 
Randomly, ONE DC7700 with a unique hard drive worked. I painstakingly checked every single driver installed and found the two that were different:
"Realtek High Definition Audio" under "Sound, video and game controllers"
"High Definition Audio Controller" under "System devices"
Pictures of the driver details for both are posted below.
I am completely at a loss as to how to accomplish this successfully, and I appreciate any help. Our school is depressingly poor, and without sound videos are completely useless to them.
Thank you in advance for your time,
Kris Brackebusch

Answer 1

Hi, Kris:
Try reinstalling W7 on one of them that doesn't have audio.
On that model, W7 should be installing a generic HD audio driver that works and then you can install the Realtek HD audio driver either from the dc7700 support page or the latest one from Realtek.
You do not need the MS UAA Bus driver, because that is only for XP.
UAA is included native to Vista and newer versions of Windows.
I do not recommend you install it in an effort to resolve the issue.
I have worked on dc7600's dc7700's and the newer Elite 8xxx models, which all have the Realtek HD audio chip.
Never had a problem getting the sound to work right from the upgrade.
The HD audio is the driver that Windows installs natively.
The Realtek HD audio driver is from Realtek.